Publications by authors named "Noriyuki Nagahara"

38 Publications

The HS-generating enzyme 3-mercaptopyruvate sulfurtransferase regulates pulmonary vascular smooth muscle cell migration and proliferation but does not impact normal or aberrant lung development.

Nitric Oxide 2021 02 15;107:31-45. Epub 2020 Dec 15.

Department of Lung Development and Remodelling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Member of the German Center for Lung Research (DZL), Parkstrasse 1, 60231, Bad Nauheim, Germany; Department of Internal Medicine (Pulmonology), University of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Justus Liebig University, Aulweg 123, 35392, Giessen, Germany; CardioPulmonary Institute, Justus Liebig University Giessen, Klinikstrasse 33, Giessen, Germany. Electronic address:

Along with nitric oxide (NO), the gasotransmitters carbon monoxide (CO) and hydrogen sulfide (HS) are emerging as potentially important players in newborn physiology, as mediators of newborn disease, and as new therapeutic modalities. Several recent studies have addressed HS in particular in animal models of bronchopulmonary dysplasia (BPD), a common complication of preterm birth where oxygen toxicity stunts lung development. In those studies, exogenous HS attenuated the impact of oxygen toxicity on lung development, and two HS-generating enzymes were documented to affect pulmonary vascular development. HS is directly generated endogenously by three enzymes, one of which, 3-mercaptopyruvate sulfurtransferase (MPST), has not been studied in the lung. In a hyperoxia-based animal model of BPD, oxygen exposure deregulated MPST expression during post-natal lung development, where MPST was localized to the smooth muscle layer of the pulmonary vessels in developing lungs. siRNA-mediated abrogation of MPST expression in human pulmonary artery smooth muscle cells in vitro limited baseline cell migration and cell proliferation, without affecting apoptosis or cell viability. In vivo, MPST was dispensable for normal lung development in Mpstmice, and MPST did not contribute to stunted lung development driven by hyperoxia exposure, assessed by design-based stereology. These data demonstrate novel roles for MPST in pulmonary vascular smooth muscle cell physiology. The potential caveats of using Mpst mice to study normal and aberrant lung development are also discussed, highlighting the possible confounding, compensatory effects of other HS-generating enzymes that are present alongside MPST in the smooth muscle compartment of developing pulmonary vessels.
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http://dx.doi.org/10.1016/j.niox.2020.12.002DOI Listing
February 2021

Activation of 3-Mercaptopyruvate Sulfurtransferase by Glutaredoxin Reducing System.

Biomolecules 2020 05 28;10(6). Epub 2020 May 28.

Isotope Research Laboratory, Nippon Medical School, 1-1-5 Sendagi Bunkyo-Ku, Tokyo 113-8602, Japan.

Glutaredoxin (EC 1.15-1.21) is known as an oxidoreductase that protects cysteine residues within proteins against oxidative stress. Glutaredoxin catalyzes an electron transfer reaction that donates an electron to substrate proteins in the reducing system composed of glutaredoxin, glutathione, glutathione reductase, and nicotinamide-adenine dinucleotide phosphate (reduced form). 3-mercaptopyruvate sulfurtransferase (EC 2.8.1.2) is a cysteine enzyme that catalyzes transsulfuration, and glutaredoxin activates 3-mercaptopyruvate sulfurtransferase in the reducing system. Interestingly, even when glutathione or glutathione reductase was absent, 3-mercaptopyruvate sulfurtransferase activity increased, probably because reduced glutaredoxin was partly present and able to activate 3-mercaptopyruvate sulfurtransferase until depletion. A study using mutant glutaredoxin1 (Cys is the binding site of glutathione and was replaced with a Ser residue) confirmed these results. Some inconsistency was noted, and glutaredoxin with higher redox potential than either 3-mercaptopyruvate sulfurtransferase or glutathione reduced 3-mercaptopyruvate sulfurtransferase. However, electron-transfer enzymatically proceeded from glutaredoxin to 3-mercaptopyruvate sulfurtransferase.
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http://dx.doi.org/10.3390/biom10060826DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7356906PMC
May 2020

HS, Polysulfides, and Enzymes: Physiological and Pathological Aspects.

Biomolecules 2020 04 21;10(4). Epub 2020 Apr 21.

Faculty of Medicine, Jagiellonian University Medical College, Kopernika 7 Cracow, 31-034 Krakow, Poland.

We have been studying the general aspects of the functions of HS and polysulfides, and the enzymes involved in their biosynthesis, for more than 20 years. Our aim has been to elucidate novel physiological and pathological functions of HS and polysulfides, and unravel the regulation of the enzymes involved in their biosynthesis, including cystathionine β-synthase (EC 4.2.1.22), cystathionine γ-lyase (EC 4.4.1.1), thiosulfate sulfurtransferase (rhodanese, EC 2.8.1.1), and 3-mercaptopyruvate sulfurtransferase (EC 2.8.1.2). Physiological and pathological functions, alternative biosynthetic processes, and additional functions of HS and polysulfides have been reported. Further, the structure and reaction mechanisms of related enzymes have also been reported. We expect this issue to advance scientific knowledge regarding the detailed functions of HS and polysulfides as well as the general properties and regulation of the enzymes involved in their metabolism. We would like to cover four topics: the physiological and pathological functions of HS and polysulfides, the mechanisms of the biosynthesis of HS and polysulfides, the properties of the biosynthetic enzymes, and the regulation of enzymatic activity. The knockout mouse technique is a useful tool to determine new physiological functions, especially those of HS and polysulfides. In the future, we shall take a closer look at symptoms in the human congenital deficiency of each enzyme. Further studies on the regulation of enzymatic activity by in vivo substances may be the key to finding new functions of HS and polysulfides.
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http://dx.doi.org/10.3390/biom10040640DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7226236PMC
April 2020

The protective role of the 3-mercaptopyruvate sulfurtransferase (3-MST)-hydrogen sulfide (HS) pathway against experimental osteoarthritis.

Arthritis Res Ther 2020 03 17;22(1):49. Epub 2020 Mar 17.

Service of Rheumatology, Department of Musculoskeletal Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland.

Background: Osteoarthritis (OA) is characterized by the formation and deposition of calcium-containing crystals in joint tissues, but the underlying mechanisms are poorly understood. The gasotransmitter hydrogen sulfide (HS) has been implicated in mineralization but has never been studied in OA. Here, we investigated the role of the HS-producing enzyme 3-mercaptopyruvate sulfurtransferase (3-MST) in cartilage calcification and OA development.

Methods: 3-MST expression was analyzed in cartilage from patients with different OA degrees, and in cartilage stimulated with hydroxyapatite (HA) crystals. The modulation of 3-MST expression in vivo was studied in the meniscectomy (MNX) model of murine OA, by comparing sham-operated to MNX knee cartilage. The role of 3-MST was investigated by quantifying joint calcification and cartilage degradation in WT and 3-MST meniscectomized knees. Chondrocyte mineralization in vitro was measured in WT and 3-MST cells. Finally, the effect of oxidative stress on 3-MST expression and chondrocyte mineralization was investigated.

Results: 3-MST expression in human cartilage negatively correlated with calcification and OA severity, and diminished upon HA stimulation. In accordance, cartilage from menisectomized OA knees revealed decreased 3-MST if compared to sham-operated healthy knees. Moreover, 3-MST mice showed exacerbated joint calcification and OA severity if compared to WT mice. In vitro, genetic or pharmacologic inhibition of 3-MST in chondrocytes resulted in enhanced mineralization and IL-6 secretion. Finally, oxidative stress decreased 3-MST expression and increased chondrocyte mineralization, maybe via induction of pro-mineralizing genes.

Conclusion: 3-MST-generated HS protects against joint calcification and experimental OA. Enhancing HS production in chondrocytes may represent a potential disease modifier to treat OA.
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http://dx.doi.org/10.1186/s13075-020-02147-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7077027PMC
March 2020

Cardiovascular phenotype of mice lacking 3-mercaptopyruvate sulfurtransferase.

Biochem Pharmacol 2020 06 4;176:113833. Epub 2020 Feb 4.

Clinical, Experimental Surgery and Translational Research Center, Biomedical Research Foundation of the Academy of Athens, Greece; Laboratory of Pharmacology, Faculty of Pharmacy, National and Kapodistrian University of Athens, Greece. Electronic address:

Rationale: Hydrogen sulfide (HS) is a physiological mediator that regulates cardiovascular homeostasis. Three major enzymes contribute to the generation of endogenously produced HS, namely cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). Although the biological roles of CSE and CBS have been extensively investigated in the cardiovascular system, very little is known about that of 3-MST. In the present study we determined the importance of 3-MST in the heart and blood vessels, using a genetic model with a global 3-MST deletion.

Results: 3-MST is the most abundant transcript in the mouse heart, compared to CSE and CBS. 3-MST was mainly localized in smooth muscle cells and cardiomyocytes, where it was present in both the mitochondria and the cytosol. Levels of serum and cardiac HS species were not altered in adult young (2-3 months old) 3-MST mice compared to WT animals. No significant changes in the expression of CSE and CBS were observed. Additionally, 3-MST mice had normal left ventricular structure and function, blood pressure and vascular reactivity. Interestingly, genetic ablation of 3-MST protected mice against myocardial ischemia reperfusion injury, and abolished the protection offered by ischemic pre- and post-conditioning. 3-MST mice showed lower expression levels of thiosulfate sulfurtransferase, lower levels of cellular antioxidants and elevated basal levels of cardiac reactive oxygen species. In parallel, 3-MST mice showed no significant alterations in endothelial NO synthase or downstream targets. Finally, in a separate cohort of older 3-MST mice (18 months old), a hypertensive phenotype associated with cardiac hypertrophy and NO insufficiency was observed.

Conclusions: Overall, genetic ablation of 3-MST impacts on the mouse cardiovascular system in an age-dependent manner. Loss of 3-MST exerts a cardioprotective role in young adult mice, while with aging it predisposes them to hypertension and cardiac hypertrophy.
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http://dx.doi.org/10.1016/j.bcp.2020.113833DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7657663PMC
June 2020

Novel Characterization of Antioxidant Enzyme, 3-Mercaptopyruvate Sulfurtransferase-Knockout Mice: Overexpression of the Evolutionarily-Related Enzyme Rhodanese.

Antioxidants (Basel) 2019 May 1;8(5). Epub 2019 May 1.

Department of Pathology and Experimental Medicine, Graduate School of Medical Science, Kumamoto University, Kumamoto 860-8556, Japan.

The antioxidant enzyme, 3-mercaptopyruvate sulfurtransferase (MST, EC 2.8.1.2) is localized in the cytosol and mitochondria, while the evolutionarily-related enzyme, rhodanese (thiosulfate sulfurtransferase, TST, EC 2.8.1.1) is localized in the mitochondria. Recently, both enzymes have been shown to produce hydrogen sulfide and polysulfide. Subcellular fractionation of liver mitochondria revealed that the TST activity ratio of MST-knockout (KO)/wild-type mice was approximately 2.5; MST activity was detected only in wild-type mice, as expected. The ratio of TST mRNA expression of KO/wild-type mice, as measured by real-time quantitative polymerase chain reaction analysis, was approximately 3.3. It is concluded that TST is overexpressed in MST-KO mice.
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http://dx.doi.org/10.3390/antiox8050116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6562775PMC
May 2019

The Effects of Genetic 3-Mercaptopyruvate Sulfurtransferase Deficiency in Murine Traumatic-Hemorrhagic Shock.

Shock 2019 04;51(4):472-478

Institute of Anesthesiological Pathophysiology and Process Engineering, University Hospital, Ulm, Germany.

Introduction: Hemorrhagic shock is a major cause of death after trauma. An additional blunt chest trauma independently contributes to mortality upon the development of an acute lung injury (ALI) by aggravating pathophysiological consequences of hemorrhagic shock. The maintenance of hydrogen sulfide availability is known to play an important role during hemorrhage and ALI. We therefore tested the impact of a genetic 3-mercaptopyruvate sulfurtransferase mutation (Δ3-MST) in a resuscitated murine model of traumatic-hemorrhagic shock.

Methods: Anesthetized wild-type (WT) and Δ3-MST mice underwent hemorrhagic shock with/without blunt chest trauma. Hemorrhagic shock was implemented for 1 h followed by retransfusion of shed blood and intensive care therapy for 4 h, including lung-protective mechanical ventilation, fluid resuscitation, and noradrenaline titrated to maintain a mean arterial pressure at least 50 mmHg. Systemic hemodynamics, metabolism, and acid-base status were assessed together with lung mechanics and gas exchange. Postmortem tissue samples were analyzed for immunohistological protein expression and mitochondrial oxygen consumption.

Results: 3-MST-deficient mice showed similar results in parameters of hemodynamics, gas exchange, metabolism, acid base status, and survival compared with the respective WT controls. Renal albumin extravasation was increased in Δ3-MST mice during hemorrhagic shock, together with a decrease of LEAK respiration in heart tissue. In contrast, mitochondrial oxygen consumption in the uncoupled state was increased in kidney and liver tissue of Δ3-MST mice subjected to the combined trauma.

Conclusions: In summary, in a resuscitated murine model of traumatic-hemorrhagic shock, 3-MST deficiency had no physiologically relevant impact on hemodynamics and metabolism, which ultimately lead to unchanged mortality regardless of an additional blunt chest trauma.
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http://dx.doi.org/10.1097/SHK.0000000000001165DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6192867PMC
April 2019

Mercaptopyruvate acts as endogenous vasodilator independently of 3-mercaptopyruvate sulfurtransferase activity.

Nitric Oxide 2018 05 13;75:53-59. Epub 2018 Feb 13.

Department of Pharmacy, School of Medicine, University of Naples, Federico II, Naples, Italy. Electronic address:

Hydrogen sulfide (HS) is produced by the action of cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) or 3-mercaptopyruvate sulfurtransferase (3-MST). 3-MST converts 3-mercaptopyruvate (MPT) to HS and pyruvate. HS is recognized as an endogenous gaseous mediator with multiple regulatory roles in mammalian cells and organisms. In the present study we demonstrate that MPT, the endogenous substrate of 3-MST, acts also as endogenous HS donor. Colorimetric, amperometric and fluorescence based assays demonstrated that MPT releases HS in vitro in an enzyme-independent manner. A functional study was performed on aortic rings harvested from C57BL/6 (WT) or 3-MST-knockout (3-MST) mice with and without endothelium. MPT relaxed mouse aortic rings in endothelium-independent manner and at the same extent in both WT and 3-MST mice. N5-(1-Iminoethyl)-l-ornithine dihydrochloride (L-NIO, an inhibitor of endothelial nitric oxide synthase) as well as 1H-[1,2,4]oxadiazolo [4,3-a]quinoxalin-1-one (ODQ, a soluble guanylyl cyclase inhibitor) did not affect MPT relaxant action. Conversely, hemoglobin (as HS scavenger), as well as glybenclamide (an ATP-dependent potassium channel blocker) markedly reduced MPT-induced relaxation. The functional data clearly confirmed a non enzymatic vascular effect of MPT. In conclusion, MPT acts also as an endogenous HS donor and not only as 3-MST substrate. MPT could, thus, be further investigated as a means to increase HS in conditions where HS bioavailability is reduced such as hypertension, coronary artery disease, diabetes or urogenital tract disease.
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http://dx.doi.org/10.1016/j.niox.2018.02.003DOI Listing
May 2018

Alternative pathway of HS and polysulfides production from sulfurated catalytic-cysteine of reaction intermediates of 3-mercaptopyruvate sulfurtransferase.

Biochem Biophys Res Commun 2018 02 10;496(2):648-653. Epub 2018 Jan 10.

Department of Analytical Biochemistry, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose-shi, Tokyo, 204-8588, Japan. Electronic address:

It has been known that hydrogen sulfide and/or polysulfides are produced from a (poly)sulfurated sulfur-acceptor substrate of 3-mercaptopyruvate sulfurtransferase (MST) via thioredoxin (Trx) reduction in vitro. In this study, we used thiosulfate as the donor substrate and the catalytic reaction was terminated on the formation of a persulfide or polysulfides. We can present alternative pathway of production of hydrogen sulfide and/or polysulfides from (poly)sulfurated catalytic-site cysteine of reaction intermediates of MST via Trx reduction. Matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometric analysis revealed that after prolonged incubation of MST with thiosulfate, a trisulfide adduct becomes predominant at the sulfurated catalytic-site cysteine. When these adducts were reduced by Trx with reducing system (MST:Escherichia coli Trx:E. coli Trx reductase:NADPH = 1:5:0.02:12.5 molar ratio), liquid chromatography with tandem mass spectrometric analysis for monobromobimane-derivatized HS revealed that HS first appeared, and then HS and HS did later. The results were confirmed by high-performance liquid chromatography-fluorescence analysis.
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http://dx.doi.org/10.1016/j.bbrc.2018.01.056DOI Listing
February 2018

Multiple role of 3-mercaptopyruvate sulfurtransferase: antioxidative function, H S and polysulfide production and possible SO production.

Br J Pharmacol 2018 02 11;175(4):577-589. Epub 2018 Jan 11.

Isotope Research Center, Nippon Medical School, Tokyo, Japan.

Rat 3-mercaptopyruvate sulfurtransferase (MPST) is a 32 808 Da simple protein. Cys is a catalytic site, and Cys and Cys are on the enzyme surface. MPST is found in all tissues, particularly in the kidneys, although the localization of its activity differs in each tissue. In this review, four functions of MPST are reviewed: (i) antioxidative function: Cys is redox-sensitive and serves as a redox-sensing switch. It is oxidized to cysteine sulfenate, which has a low redox potential, upon which the enzyme is inactivated. Then, reduced thioredoxin (Trx) with a reducing system (Trx reductase and NADPH) reduces the sulfenate to restore activity; meanwhile, Cys and Cys form an intermolecular disulfide bond, which serves as another redox-sensing switch. Consequently, Trx specifically cleaves the intermolecular disulfide bond by converting it from the inactive form (dimer) to the active form (monomer). (ii) Hydrogen sulfide and polysulfide production: hydrogen sulfide is produced via reduction of the persulfurated sulfur-acceptor substrate by reduced Trx or Trx with a reducing system; as an alternative process, stable polysulfurated or persulfurated Cys as a reaction intermediate is reduced by Trx with a reducing system to release hydrogen sulfide and polysulfides. (iii) Possible sulfur oxide production: sulfur oxides (SO, SO and SO ) can be produced in the redox cycle of sulfane sulfur formed at the catalytic site Cys (Cys-SO , Cys-SO and Cys-SO ) as reaction intermediates and released by reduced Trx or Trx with a reducing system. (iv) Possible anxiolytic-like effects: MPST-knockout mice exhibited anxiolytic-like effects.
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http://dx.doi.org/10.1111/bph.14100DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5786452PMC
February 2018

Expression of 3-Mercaptopyruvate Sulfurtransferase in the Mouse.

Molecules 2016 Dec 11;21(12). Epub 2016 Dec 11.

Department of Pathology and Experimental Medicine, Kumamoto University Graduate School of Medical Sciences, 1-1-1 Honjo Chuo-ku, Kumamoto 860-8556, Japan.

3-Mercaptopyruvate sulfurtransferase (MST) is one of the principal enzymes for the production of hydrogen sulfide and polysulfides in mammalians, and emerging evidence supports the physiological significance of MST. As a fundamental study of the physiology and pathobiology of MST, it is necessary to establish the tissue distribution of MST in mice. In the present study, the expression of MST in various organs of adult and fetal mice was analyzed by Western blotting and enzyme-immunohistochemistry. Moreover, the histology of MST gene-deficient mice was examined. Western blotting revealed that all organs examined had MST. The brain, liver, kidneys testes, and endocrine organs contained large amounts of MST, but the lungs, spleen, thymus, and small intestine did not. Immunohistochemically, the MST expression pattern varies in a cell-specific manner. In the brain, neural and glial cells are positively stained; in the lung, bronchiolar cells are preferentially stained; in the liver, hepatocytes around central veins are more strongly stained; renal convoluted cells are strongly stained; and pancreatic islets are strongly stained. Fetal tissues were studied, and MST expression was found to be similar before and after birth. Histological observation revealed no remarkable findings in MST gene-deficient mice. The present study revealed fundamental information regarding the MST expression of various organs in adult and fetal mice, and the morphological phenotype of MST gene-deficient mice.
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http://dx.doi.org/10.3390/molecules21121707DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6273466PMC
December 2016

Identification of H2S3 and H2S produced by 3-mercaptopyruvate sulfurtransferase in the brain.

Sci Rep 2015 Oct 6;5:14774. Epub 2015 Oct 6.

Department of Molecular Pharmacology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan.

Hydrogen polysulfides (H2Sn) have a higher number of sulfane sulfur atoms than hydrogen sulfide (H2S), which has various physiological roles. We recently found H2Sn in the brain. H2Sn induced some responses previously attributed to H2S but with much greater potency than H2S. However, the number of sulfur atoms in H2Sn and its producing enzyme were unknown. Here, we detected H2S3 and H2S, which were produced from 3-mercaptopyruvate (3 MP) by 3-mercaptopyruvate sulfurtransferase (3MST), in the brain. High performance liquid chromatography with fluorescence detection (LC-FL) and tandem mass spectrometry (LC-MS/MS) analyses showed that H2S3 and H2S were produced from 3 MP in the brain cells of wild-type mice but not 3MST knockout (3MST-KO) mice. Purified recombinant 3MST and lysates of COS cells expressing 3MST produced H2S3 from 3 MP, while those expressing defective 3MST mutants did not. H2S3 was localized in the cytosol of cells. H2S3 was also produced from H2S by 3MST and rhodanese. H2S2 was identified as a minor H2Sn, and 3 MP did not affect the H2S5 level. The present study provides new insights into the physiology of H2S3 and H2S, as well as novel therapeutic targets for diseases in which these molecules are involved.
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http://dx.doi.org/10.1038/srep14774DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4594004PMC
October 2015

Sex differences in shotgun proteome analyses for chronic oral intake of cadmium in mice.

PLoS One 2015 20;10(3):e0121819. Epub 2015 Mar 20.

Isotope Research Center, Nippon Medical School, Bunkyo-ku, Tokyo, Japan.

Environmental diseases related to cadmium exposure primarily develop owing to industrial wastewater pollution and/or contaminated food. In regions with high cadmium exposure in Japan, cadmium accumulation occurs primarily in the kidneys of individuals who are exposed to the metal. In contrast, in the itai-itai disease outbreak that occurred in the Jinzu River basin in Toyama Prefecture in Japan, cadmium primarily accumulated in the liver. On the other hand, high concentration of cadmium caused renal tubular disorder and osteomalacia (multiple bone fracture), probably resulting from the renal tubular dysfunction and additional pathology. In this study, we aimed to establish a mouse model of chronic cadmium intake. We administered cadmium-containing drinking water (32 mg/l) to female and male mice ad libitum for 11 weeks. Metal analysis using inductively coupled plasma mass spectrometry revealed that cadmium accumulated in the kidneys (927 x 10 + 185 ng/g in females and 661 x 10 + 101 ng/g in males), liver (397 x 10 + 199 ng/g in females and 238 x 10 + 652 ng/g in males), and thyroid gland (293 + 93.7 ng/g in females and 129 + 72.7 ng/g in males) of mice. Female mice showed higher cadmium accumulation in the kidney, liver, and thyroid gland than males did (p = 0.00345, p = 0.00213, and p = 0.0331, respectively). Shotgun proteome analyses after chronic oral administration of cadmium revealed that protein levels of glutathione S-transferase Mu2, Mu4, and Mu7 decreased in the liver, and those of A1 and A2 decreased in the kidneys in both female and male mice.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0121819PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4368563PMC
February 2016

Redox regulation of mammalian 3-mercaptopyruvate sulfurtransferase.

Methods Enzymol 2015 20;554:229-54. Epub 2015 Jan 20.

Department of Pharmacology, Nippon Medical School, Tokyo, Japan.

A cystine-catabolizing enzyme, 3-mercaptopyruvate sulfurtransferase catalyzes the trans-sulfuration reaction of mercaptopyruvate or thiosulfate to thiol-containing compounds or cyanide. During the catalytic process, persulfide is formed at the catalytic site cysteine residue and a sulfur-acceptor substrate donates the outer sulfur of the persulfide to form a new persulfide molecule. Subsequently, the molecule can be reduced by thioredoxin to form hydrogen sulfide. The enzyme is regulated by redox changes via two redox-sensing molecular switches consisting redox-sensitive cysteine residues. One switch is the catalytic cysteine in itself, which is oxidized to form a cysteine-sulfenate resulting in inhibition of catalytic activity. The sulfenate can be reduced by thioredoxin resulting in restoration of the activity. The redox potential of sulfenate is lower than that of glutathione and greater than that of thioredoxin. The other switch involves cysteine residues positioned on the surface of the enzyme. The oxidation the intermolecular disulfide linkage at these cysteine residues, leading to dimer formation, inhibits enzyme activity. On the other hand, reduction-associated monomer formation increases catalytic activity. Thioredoxin reduces the disulfide bond more effectively than dithiothreitol, although the specificity mechanism has not been identified. Congenital defects in this enzyme result in, mercaptolactate-cysteine disulfiduria associated with or without mental retardation. However, the pathogenesis has not been identified. Because 3-mercaptopyruvate sulfurtransferase serves as a cellular antioxidative protein, the other biological functions related to the inhabitant disease are being investigated.
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http://dx.doi.org/10.1016/bs.mie.2014.11.017DOI Listing
November 2015

Identification of nuclear phosphoproteins as novel tobacco markers in mouse lung tissue following short-term exposure to tobacco smoke.

FEBS Open Bio 2014 23;4:746-54. Epub 2014 Aug 23.

Department of Pathology and Experimental Medicine, Kumamoto University, 1-1-1, Honjo, Kumamoto 860-8556, Japan.

Smoking is a risk factor for lung diseases, including chronic obstructive pulmonary disease and lung cancer. However, the molecular mechanisms mediating the progression of these diseases remain unclear. Therefore, we sought to identify signaling pathways activated by tobacco-smoke exposure, by analyzing nuclear phosphoprotein expression using phosphoproteomic analysis of lung tissue from mice exposed to tobacco smoke. Sixteen mice were exposed to tobacco smoke for 1 or 7 days, and the expression of phosphorylated peptides was analyzed by mass spectrometry. A total of 253 phosphoproteins were identified, including FACT complex subunit SPT16 in the 1-day exposure group, keratin type 1 cytoskeletal 18 (K18), and adipocyte fatty acid-binding protein, in the 7-day exposure group, and peroxiredoxin-1 (OSF3) and spectrin β chain brain 1 (SPTBN1), in both groups. Semi-quantitative analysis of the identified phosphoproteins revealed that 33 proteins were significantly differentially expressed between the control and exposed groups. The identified phosphoproteins were classified according to their biological functions. We found that the identified proteins were related to inflammation, regeneration, repair, proliferation, differentiation, morphogenesis, and response to stress and nicotine. In conclusion, we identified proteins, including OSF3 and SPTBN1, as candidate tobacco smoke-exposure markers; our results provide insights into the mechanisms of tobacco smoke-induced diseases.
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http://dx.doi.org/10.1016/j.fob.2014.08.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4208089PMC
October 2014

Proteome analysis for downstream targets of oncogenic KRAS--the potential participation of CLIC4 in carcinogenesis in the lung.

PLoS One 2014 4;9(2):e87193. Epub 2014 Feb 4.

Department of Pathology, Yokohama City University Graduate School of Medicine, 3-9, Future, Kanazawa-ku, Yokohama, Japan.

This study investigated the proteome modulated by oncogenic KRAS in immortalized airway epithelial cells. Chloride intracellular channel protein 4 (CLIC4), S100 proteins (S100A2 and S100A11), tropomyosin 2, cathepsin L1, integrinsα3, eukaryotic elongation factor 1, vimentin, and others were discriminated. We here focused on CLIC4 to investigate its potential involvement in carcinogenesis in the lung because previous studies suggested that some chloride channels and chloride channel regulators could function as tumor suppressors. CILC4 protein levels were reduced in some lung cancer cell lines. The restoration of CLIC4 in lung cancer cell lines in which CLIC4 expression was reduced attenuated their growth activity. The immunohistochemical expression of the CLIC4 protein was weaker in primary lung cancer cells than in non-tumorous airway epithelial cells and was occasionally undetectable in some tumors. CLIC4 protein levels were significantly lower in a subtype of mucinous ADC than in others, and were also significantly lower in KRAS-mutated ADC than in EGFR-mutated ADC. These results suggest that the alteration in CLIC4 could be involved in restrictedly the development of a specific fraction of lung adenocarcinomas. The potential benefit of the proteome modulated by oncogenic KRAS to lung cancer research has been demonstrated.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0087193PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3913595PMC
December 2014

Antioxidant enzyme, 3-mercaptopyruvate sulfurtransferase-knockout mice exhibit increased anxiety-like behaviors: a model for human mercaptolactate-cysteine disulfiduria.

Sci Rep 2013 ;3:1986

Isotope Research Center, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.

Human mercaptolactate-cysteine disulfiduria (MCDU) was first recognized and reported in 1968. Most cases of MCDU are associated with mental retardation, while the pathogenesis remains unknown. To investigate it, we generated homozygous 3-mercaptopyruvate sulfurtransferase (MST: EC 2.8.1.2) knockout (KO) mice using C57BL/6 embryonic stem cells as an animal model. The MST-KO mice showed significantly increased anxiety-like behaviors with an increase in serotonin level in the prefrontal cortex (PFC), but not with abnormal morphological changes in the brain. MCDU can be caused by loss in the functional diversity of MST; first, MST functions as an antioxidant protein. MST possessing 2 redox-sensing molecular switches maintains cellular redox homeostasis. Second, MST can produce H2S (or HS(-)). Third, MST can also produce SOx. It is concluded that behavioral abnormality in MST-KO mice is caused by MST function defects such as an antioxidant insufficiency or a new transducer, H2S (or HS(-)) and/or SOx deficiency.
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http://dx.doi.org/10.1038/srep01986DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3680806PMC
June 2014

A novel fluorescence in situ hybridization assay for synovial sarcoma.

Pathol Res Pract 2013 May 15;209(5):309-13. Epub 2013 Mar 15.

Division of Pathology, Kanagawa Children's Medical Center, Yokohama, Japan.

Synovial sarcoma, which is difficult to diagnose precisely, is one of the most common childhood nonrhabdomyosarcoma soft-tissue sarcomas. The purpose of this study is to develop new molecular cytogenetic assay. We used two sets of two-color break-apart FISH probes, flanking either the SSX1/SSX4 or SSX2 locus. Each set of probes is composed of differentially labeled DNA fragments complementary to sequences proximal or distal to the break point within the SSX1/SSX4 or SSX2 locus, which are applied separately to histopathological sections. Interphase nuclei containing a translocation that disrupts either SSX1, SSX2, or SSX4 locus will display two single-color signals that have "broken apart" from each other. We applied it to two synovial sarcoma cell lines and clinical samples. This assay can detect translocation at either SSX1/SSX4, or SSX2 locus on interphase spread prepared from synovial sarcoma cell line and histopathological sections, which is sufficient to diagnose as synovial sarcoma. Our new FISH assay has several advantages, including its applicability to paraffin-embedded samples, discrimination of the SS18-SSX1 and SS18-SSX2 translocations particularly in cases with aneuploidy, and potentially detecting translocations in all cases of synovial sarcoma, even with variant translocations. Our strategy will improve the accuracy of diagnoses, thereby facilitating appropriate treatment planning.
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http://dx.doi.org/10.1016/j.prp.2013.02.013DOI Listing
May 2013

Inhaled aerosolized insulin ameliorates hyperglycemia-induced inflammatory responses in the lungs in an experimental model of acute lung injury.

Crit Care 2013 Apr 28;17(2):R83. Epub 2013 Apr 28.

Introduction: Previous studies have shown that patients with diabetes mellitus appear to have a lower prevalence of acute lung injury. We assumed that insulin prescribed to patients with diabetes has an anti-inflammatory property and pulmonary administration of insulin might exert beneficial effects much more than intravenous administration.

Methods: Twenty-eight mechanically ventilated rabbits underwent lung injury by saline lavage, and then the animals were allocated into a normoglycemia group (NG), a hyperglycemia group (HG), an HG treated with intravenous insulin (HG-VI) group or an HG treated with aerosolized insulin (HG-AI) group with continuous infusion of different fluid solutions and treatments: normal saline, 50% glucose, 50% glucose with intravenous insulin, or 50% glucose with inhaled aerosolized insulin, respectively. After four hours of treatment, the lungs and heart were excised en bloc, and then high-mobility group B1 concentration in bronchoalveolar lavage fluid, interleukin-8 and toll-like receptor 4 mRNA expression in bronchoalveolar lavage fluid cells, and lung myeloperoxidase activity were measured.

Results: Treatment with both aerosolized insulin and intravenous insulin attenuated toll-like receptor 4 mRNA expressions in the bronchoalveolar lavage fluid cells. Interleukin-8 and toll-like receptor 4 mRNA expression was significantly lower in the HG-AI group than in the HG-IV group. The lung myeloperoxidase activity in the normal healthy group showed significantly lower levels compared to the NG group but not different compared to those of the HG, HG-VI and HG-AI groups.

Conclusions: The results suggest that insulin attenuates inflammatory responses in the lungs augmented by hyperglycemia in acute lung injury and the insulin's efficacy may be better when administered by aerosol.
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http://dx.doi.org/10.1186/cc12697DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4057452PMC
April 2013

A novel pathway for the production of hydrogen sulfide from D-cysteine in mammalian cells.

Nat Commun 2013 ;4:1366

Department of Molecular Pharmacology, National Institute of Neuroscience, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan.

In eukaryotes, hydrogen sulphide acts as a signalling molecule and cytoprotectant. Hydrogen sulphide is known to be produced from L-cysteine by cystathionine β-synthase, cystathionine γ-lyase and 3-mercaptopyruvate sulfurtransferase coupled with cysteine aminotransferase. Here we report an additional biosynthetic pathway for the production of hydrogen sulphide from D-cysteine involving 3-mercaptopyruvate sulfurtransferase and D-amino acid oxidase. Unlike the L-cysteine pathway, this D-cysteine-dependent pathway operates predominantly in the cerebellum and the kidney. Our study reveals that administration of D-cysteine protects primary cultures of cerebellar neurons from oxidative stress induced by hydrogen peroxide and attenuates ischaemia-reperfusion injury in the kidney more than L-cysteine. This study presents a novel pathway of hydrogen sulphide production and provides a new therapeutic approach to deliver hydrogen sulphide to specific tissues.
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http://dx.doi.org/10.1038/ncomms2371DOI Listing
June 2013

Regulation of mercaptopyruvate sulfurtransferase activity via intrasubunit and intersubunit redox-sensing switches.

Antioxid Redox Signal 2013 Nov 19;19(15):1792-802. Epub 2012 Dec 19.

Isotope Research Center, Nippon Medical School , Tokyo, Japan .

Significance: Redox regulates 3-mercaptopyruvate sulfurtransferase (MST, EC 2.8.1.2) activity via both intermolecular and intramolecular redox-sensing switches. The intermolecular switch comprises an intermolecular disulfide bond that forms a homodimer. On the other hand, the intramolecular switch is a catalytic site cysteine that forms a low redox potential sulfenate. Both switches are reduced by thioredoxin with the reducing system, including thioredoxin reductase and NADPH, and to a much lesser extent by reduced glutathione. It becomes clear that MST serves as not only an enzyme in cysteine catabolism, but also as an antioxidant protein.

Recent Advances: New findings have been accumulated that, in the catalytic process of MST, hydrogen peroxide is possibly produced by persulfide of the sulfur-accepted substrate and sulfur oxides are possibly produced in the redox cycle of persulfide formed at the catalytic site cysteine of the reaction intermediate. Further, we recently succeeded to produce MST knockout (KO) mice.

Critical Issues: A congenital metabolic disorder, mercaptolactate-cysteine disulfiduria (MCDU) is caused by MST defect with or without mental retardation. The MST KO mouse is just a MCDU model. Recent findings suggest that hydrogen sulfide and/or sulfur oxides are involved in the neurobehavioral changes in MCDU.

Future Directions: We investigate the pathogenesis of MCDU by performing a comprehensive analysis of the MST KO mice to clarify the functional diversity of MST and biological importance of hydrogen sulfide and sulfur oxides in the brain.
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http://dx.doi.org/10.1089/ars.2012.5031DOI Listing
November 2013

Catalytic site cysteines of thiol enzyme: sulfurtransferases.

J Amino Acids 2011 28;2011:709404. Epub 2010 Dec 28.

Department of Environmental Medicine, Nippon Medical School, 1-1-5 Sendagi Bunkyo-ku, Tokyo 113-8602, Japan.

Thiol enzymes have single- or double-catalytic site cysteine residues and are redox active. Oxidoreductases and isomerases contain double-catalytic site cysteine residues, which are oxidized to a disulfide via a sulfenyl intermediate and reduced to a thiol or a thiolate. The redox changes of these enzymes are involved in their catalytic processes. On the other hand, transferases, and also some phosphatases and hydrolases, have a single-catalytic site cysteine residue. The cysteines are redox active, but their sulfenyl forms, which are inactive, are not well explained biologically. In particular, oxidized forms of sulfurtransferases, such as mercaptopyruvate sulfurtransferase and thiosulfate sulfurtransferase, are not reduced by reduced glutathione but by reduced thioredoxin. This paper focuses on why the catalytic site cysteine of sulfurtransferase is redox active.
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http://dx.doi.org/10.4061/2011/709404DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3276061PMC
August 2012

Is novel signal transducer sulfur oxide involved in the redox cycle of persulfide at the catalytic site cysteine in a stable reaction intermediate of mercaptopyruvate sulfurtransferase?

Antioxid Redox Signal 2012 Apr 11;16(8):747-53. Epub 2012 Jan 11.

Department of Environmental Medicine, Nippon Medical School, Tokyo, Japan.

Abstract In transsulfuration reaction catalyzed by rat mercaptopyruvate sulfurtransferase (MST), a stable persulfide is formed at the catalytic site cysteine Cys(247) as a reaction intermediate. The outer sulfur atom is donated by the substrate, thiosulfate, or by mercaptopyruvate. MST serves as a thioredoxin-dependent antioxidant possessing self-regulated enzymatic activity. After oxidation of persulfurated MST by treatment with hydrogen peroxide, mass spectrometric analysis showed that the outer sulfur atom of the persulfide is oxidized to form Cys-thiosulfenate (Cys-Sγ-SO(-)), Cys-thiosulfinate (Cys-Sγ-SO(2)(-)), and Cys-thiosulfonate (Cys-Sγ-SO(3)(-)). Next, sulfur acceptor substrates including reduced thioredoxin convert all modified cysteines to nonmodified cysteines. Another sulfur acceptor substrate, cyanide, also converted these cysteines via cyanolysis. Thus, sulfur oxides are suggested to release in the redox cycle of persulfide of MST.
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http://dx.doi.org/10.1089/ars.2011.4468DOI Listing
April 2012

Hydrogen sulfide protects the retina from light-induced degeneration by the modulation of Ca2+ influx.

J Biol Chem 2011 Nov 20;286(45):39379-86. Epub 2011 Sep 20.

Department of Molecular Pharmacology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan.

Hydrogen sulfide (H(2)S) has recently been recognized as a signaling molecule as well as a cytoprotectant. Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) are well-known as H(2)S-producing enzymes. We recently demonstrated that 3-mercaptopyruvate sulfurtransferase (3MST) along with cysteine aminotransferase (CAT) produces H(2)S in the brain and in vascular endothelium. However, the cellular distribution and regulation of these enzymes are not well understood. Here we show that 3MST and CAT are localized to retinal neurons and that the production of H(2)S is regulated by Ca(2+); H(2)S, in turn, regulates Ca(2+) influx into photoreceptor cells by activating vacuolar type H(+)-ATPase (V-ATPase). We also show that H(2)S protects retinal neurons from light-induced degeneration. The excessive levels of light exposure deteriorated photoreceptor cells and increased the number of TUNEL- and 8-hydroxy-2'-deoxyguanosine (8-OHdG)-positive cells. Degeneration was greatly suppressed in the retina of mice administered with NaHS, a donor of H(2)S. The present study provides a new insight into the regulation of H(2)S production and the modulation of the retinal transmission by H(2)S. It also shows a cytoprotective effect of H(2)S on retinal neurons and provides a basis for the therapeutic target for retinal degeneration.
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http://dx.doi.org/10.1074/jbc.M111.298208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3234762PMC
November 2011

Thioredoxin and dihydrolipoic acid are required for 3-mercaptopyruvate sulfurtransferase to produce hydrogen sulfide.

Biochem J 2011 Nov;439(3):479-85

Department of Molecular Pharmacology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Ogawa-Higashi, Kodaira, Tokyo, Japan.

H2S (hydrogen sulfide) has recently been recognized as a signalling molecule as well as a cytoprotectant. We recently demonstrated that 3MST (3-mercaptopyruvate sulfurtransferase) produces H2S from 3MP (3-mercaptopyruvate). Although a reducing substance is required for an intermediate persulfide at the active site of 3MST to release H2S, the substance has not been identified. In the present study we show that Trx (thioredoxin) and DHLA (dihydrolipoic acid) associate with 3MST to release H2S. Other reducing substances, such as NADPH, NADH, GSH, cysteine and CoA, did not have any effect on the reaction. We also show that 3MST produces H2S from thiosulfate. The present study provides a new insight into a mechanism for the production of H2S by 3MST.
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http://dx.doi.org/10.1042/BJ20110841DOI Listing
November 2011

Protein cysteine modifications: (2) reactivity specificity and topics of medicinal chemistry and protein engineering.

Curr Med Chem 2009 ;16(34):4490-501

Department of Environmental Medicine, Nippon Medical School, 1-1-5 Sendagi Bunkyo-ku, Tokyo 113-8602, Japan.

Cysteine (cysteinyl residue) modifications in proteins result in diversity in protein functions. The reaction specificity of a protein with a modified cysteine residue is determined by the overall conditions of the protein, including the spatial position of the cysteine residue, electrostatic interactions between cysteine residue and other charged residues, spatial interactions between the cysteine residue and a chemical compound, electrophilicity of the chemical compound, and the pH of the solution. In cysteine-dependant enzymes, each specific type of cysteine modification characterizes the catalytic mechanism of the enzyme. Recently, the catalytic mechanisms of peroxiredoxins and cysteine proteases, which contain a cysteine residue(s) in their catalytic sites, have been elucidated. In the catalytic process of peroxiredoxins, a sulfenyl intermediate is formed by oxidation of the catalytic cysteine residue. On the other hand, in cysteine proteases, the catalytic cysteine residue reacts with the carboxyl carbon of a peptide substrate to form an intermediate complex via S-alkylation. In this review, we introduce the most current information on the applications of cysteine thiol chemistry for in vitro glycoprotein synthesis. Recently, a glycoprotein (monocyte chemotactic protein-3), containing an intact human complex-type sialyloligosaccharide has been chemically synthesized. The procedure used for this could have applications in the development of new protein-based drugs, including antineoplastic drugs and antibiotics. It can also potentially be applied for improving the half-life and reducing the toxicity of these drugs, and for preventing the development of multidrug resistance.
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http://dx.doi.org/10.2174/092986709789760643DOI Listing
February 2010

Vascular endothelium expresses 3-mercaptopyruvate sulfurtransferase and produces hydrogen sulfide.

J Biochem 2009 Nov 15;146(5):623-6. Epub 2009 Jul 15.

National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan.

Hydrogen sulfide (H(2)S) has been recognized as a smooth muscle relaxant. Cystathionine gamma-lyase, which is localized to smooth muscle, is thought to be the major H(2)S-producing enzyme in the thoracic aorta. Here we show that 3-mercaptopyruvate sulfurtransferase (3MST) and cysteine aminotransferase (CAT) are localized to vascular endothelium in the thoracic aorta and produce H(2)S. Both 3MST and CAT were localized to endothelium. Lysates of vascular endothelial cells produced H(2)S from cysteine and alpha-ketoglutarate. The present study provides a new insight into the production and release of H(2)S as a smooth muscle relaxant from vascular endothelium.
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http://dx.doi.org/10.1093/jb/mvp111DOI Listing
November 2009

A novel mercaptopyruvate sulfurtransferase thioredoxin-dependent redox-sensing molecular switch: a mechanism for the maintenance of cellular redox equilibrium.

Mini Rev Med Chem 2008 Jun;8(6):585-9

Department of Environmental Medicine, Nippon Medical School, 1-1-5 Sendagi, Tokyo 113-8602, Japan.

An intermolecular disulfide bond serves as a thioredoxin-dependent redox-sensing switch for the regulation of the enzymatic activity of 3-mercaptopyruvate sulfurtransferase (MST, EC.2.8.1.2). A cysteine residue on the surface of each subunit was oxidized to form an intersubunit disulfide bond so as to decrease MST activity, and thioredoxin-specific conversion of a dimer to a monomer increased MST activity. Further, a low redox potential sulfenate was reversibly formed at a catalytic site cysteine so as to inhibit MST, and thioredoxin-dependent reduction of the sulfenate restored the MST activity. Concludingly, MST partly contributes to the maintenance of cellular redox homeostasis via exerting control over cysteine catabolism.
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http://dx.doi.org/10.2174/138955708784534409DOI Listing
June 2008

Thioredoxin-dependent enzymatic activation of mercaptopyruvate sulfurtransferase. An intersubunit disulfide bond serves as a redox switch for activation.

J Biol Chem 2007 Jan 27;282(3):1561-9. Epub 2006 Nov 27.

Department of Environmental Medicine, Nippon Medical School, Tokyo, Japan.

Rat 3-mercaptopyruvate sulfurtransferase (MST) contains three exposed cysteines as follows: a catalytic site cysteine, Cys(247), in the active site and Cys(154) and Cys(263) on the surface of MST. The corresponding cysteine to Cys(263) is conserved in mammalian MSTs, and Cys(154) is a unique cysteine. MST has monomer-dimer equilibrium with the assistance of oxidants and reductants. The monomer to dimer ratio is maintained at approximately 92:8 in 0.2 m potassium phosphate buffer containing no reductants under air-saturated conditions; the dimer might be symmetrical via an intersubunit disulfide bond between Cys(154) and Cys(154) and between Cys(263) and Cys(263), or asymmetrical via an intersubunit disulfide bond between Cys(154) and Cys(263). Escherichia coli reduced thioredoxin (Trx) cleaved the intersubunit disulfide bond to activate MST to 2.3- and 4.9-fold the levels of activation of dithiothreitol (DTT)-treated and DTT-untreated MST, respectively. Rat Trx also activated MST. On the other hand, reduced glutathione did not affect MST activity. E. coli C35S Trx, in which Cys(35) was replaced with Ser, formed some adducts with MST and activated MST after treatment with DTT. Thus, Cys(32) of E. coli Trx reacted with the redox-active cysteines, Cys(154) and Cys(263), by forming an intersubunit disulfide bond and a sulfenyl Cys(247). A consecutively formed disulfide bond between Trx and MST must be cleaved for the activation. E. coli C32S Trx, however, did not activate MST. Reduced Trx turns on a redox switch for the enzymatic activation of MST, which contributes to the maintenance of cellular redox homeostasis.
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http://dx.doi.org/10.1074/jbc.M605931200DOI Listing
January 2007

The mercaptopyruvate pathway in cysteine catabolism: a physiologic role and related disease of the multifunctional 3-mercaptopyruvate sulfurtransferase.

Curr Med Chem 2006 ;13(10):1219-30

Department of Environmental Medicine, Nippon Medical School, Tokyo 113-8602, Japan.

The conversion of cysteine to 3-sulfino-alanine is a major pathway in cysteine catabolism. Cysteine dioxygenase catalyzes the reaction and dietary intake of the essential amino acid methionine and the semi-essential amino acid cysteine increases the level of this enzyme by suppressing enzyme degradation via polyubiquitination. The production of cellular antioxidants such as glutathione, thioredoxin, and their families is important in cysteine metabolism, and these cellular antioxidants have critical roles in the maintenance of the cellular redox status. The mercaptopyruvate pathway, in which cysteine or aspartate transaminase catalyzes the transamination from cysteine to 3-mercaptopyruvate and then 3-mercaptopyruvate sulfurtransferase catalyzes the transsulfuration from 3-mercaptopyruvate to pyruvate, also contributes to maintain the cellular redox. 3-Mercaptopyruvate sulfurtransferase serves as an antioxidant protein: when the enzyme is exposed to stoichiometric amounts of the oxidant hydrogen peroxide, it is inhibited via the formation of low redox sulfenate at the catalytic site cysteine. On the other hand, activity is restored by the reductant dithiothreitol or reduced thioredoxin. 3-Mercaptopyruvate sulfurtransferase also detoxifies cyanide via transsulfuration from a stable persulfide at the catalytic site cysteine, a reaction intermediate, suggesting that cyanide detoxification is not necessarily an enzymatic reaction. Furthermore, a congenital defect of the enzyme causes mercaptolactate-cysteine disulfiduria associated with or without mental retardation, although the pathogenesis remains unclear. These facts suggest that 3-mercaptopyruvate sulfurtransferase has physiologic roles as an antioxidant and a cyanide antidote; is essential for neural function, and participates in cysteine degradation.
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http://dx.doi.org/10.2174/092986706776360914DOI Listing
December 2006
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