Publications by authors named "Hiroyuki Itamura"

7 Publications

  • Page 1 of 1

Recombinant expression, purification, and characterization of polyphenol oxidase 2 (VvPPO2) from "Shine Muscat" (Vitis labruscana Bailey × Vitis vinifera L.).

Biosci Biotechnol Biochem 2017 Dec 11;81(12):2330-2338. Epub 2017 Oct 11.

d Faculty of Life and Environmental Science , Shimane University , Matsue , Japan.

Polyphenol oxidases (PPOs) catalyze browning reactions in various plant organs, therefore controlling the reactions is important for the food industry. PPOs have been assumed to be involved in skin browning of white grape cultivars; however, the molecular mechanism underlying PPO-mediated browning process remains elusive. We have recently identified a new PPO gene named VvPPO2 from "Shine Muscat" (Vitis labruscana Bailey × V. vinifera L.), and have shown that the gene is transcribed at a higher level than the previously identified VvPPO1 in browning, physiologically disordered berry skins at the maturation stage. In this study, we expressed VvPPO2 in Escherichia coli and, using the purified preparation, revealed unique physicochemical characteristics of the enzyme. Our study opens up a way to not only understand the berry skin browning process but also to elucidate the enzymatic maturation process of grape PPOs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/09168451.2017.1381017DOI Listing
December 2017

Effects of Applied Nitrogen Amounts on the Functional Components of Mulberry (Morus alba L.) Leaves.

J Agric Food Chem 2016 Sep 12;64(37):6923-9. Epub 2016 Sep 12.

Faculty of Life and Environmental Science, Shimane University , 1060 Nishikawatsu-cho, Matsue, Shimane 690-8504, Japan.

This study investigated the effects of applied nitrogen amounts on specific functional components in mulberry (Morus alba L.) leaves. The relationships between mineral elements and the functional components in mulberry leaves were examined using mulberry trees cultivated in different soil conditions in four cultured fields. Then, the relationships between the nitrogen levels and the leaf functional components were studied by culturing mulberry in plastic pots and experimental fields. In the common cultured fields, total nitrogen was negatively correlated with the chlorogenic acid content (R(2) = -0.48) and positively correlated with the 1-deoxynojirimycin content (R(2) = 0.60). Additionally, differences in nitrogen fertilizer application levels affected each functional component in mulberry leaves. For instance, with increased nitrogen levels, the chlorogenic acid and flavonol contents significantly decreased, but the 1-deoxynojirimycin content significantly increased. Selection of the optimal nitrogen application level is necessary to obtain the desired functional components from mulberry leaves.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jafc.6b01922DOI Listing
September 2016

Effect of solar radiation on the functional components of mulberry (Morus alba L.) leaves.

J Sci Food Agric 2016 Aug 15;96(11):3915-21. Epub 2016 Feb 15.

Shimane University, 1060 Nishikawatsu-cho, Matsue, Shimane, 690-8504, Japan.

Background: The functional components of mulberry leaves have attracted the attention of the health food industry, and increasing their concentrations is an industry goal. This study investigated the effects of solar radiation, which may influence the production of flavonol and 1-deoxynojirimycin (DNJ) functional components in mulberry leaves, by comparing a greenhouse (poor solar radiation) and outdoor (rich solar radiation) setting.

Results: The level of flavonol in leaves cultivated in the greenhouse was markedly decreased when compared with those cultivated outdoors. In contrast, the DNJ content in greenhouse-cultivated plants was increased only slightly when compared with those cultivated outdoors. Interestingly, the flavonol content was markedly increased in the upper leaves of mulberry trees that were transferred from a greenhouse to the outdoors compared with those cultivated only in the outdoors.

Conclusion: Solar radiation conditions influence the synthesis of flavonol and DNJ, the functional components of mulberry leaves. Under high solar radiation, the flavonol level becomes very high but the DNJ level becomes slightly lower, suggesting that the impact of solar radiation is great on flavonol but small on DNJ synthesis. © 2016 Society of Chemical Industry.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jsfa.7614DOI Listing
August 2016

Varietal differences in the flavonol content of mulberry (Morus spp.) leaves and genetic analysis of quercetin 3-(6-malonylglucoside) for component breeding.

J Agric Food Chem 2013 Sep 10;61(38):9140-7. Epub 2013 Sep 10.

Shimane Agricultural Technology Center , 2440 Ashiwata-cho, Izumo, Shimane 693-0035, Japan.

The varietal differences in the flavonol glycosides rutin, isoquercitrin, kaempferol 3-(6-rhamnosylglucoside), quercetin 3-(6-malonylglucoside), astragalin, quercetin 3-(6-acetylglucoside), and kaempferol 3-(6-malonylglucoside) contained in mulberry leaves were elucidated. This information was used for breeding mulberry cultivars with a high concentration of functional components. The flavonol content, composition, and proportion in leaves varied widely. 'Kobuchizawa 1' had the highest level of total flavonols (1819 mg/100 g of dry weight), 5 times higher than that of 'Mikurasima 15' (393 mg/100 g of dry weight). Quercetin 3-(6-malonylglucoside) was the most abundant flavonol, although it was not found in all cultivars. Quercetin 3-(6-acetylglucoside) was only found in 'Keguwa'. From the quercetin 3-(6-malonylglucoside) content in crossbred offspring, malonyltransferase, an enzyme involved in quercetin 3-(6-malonylglucoside) synthesis, was acquired according to Mendelian inheritance. An offspring with a higher quercetin 3-(6-malonylglucoside) level than both parents was obtained from the crossing. This suggested that crossbreeding was effective for acquiring cultivars with a higher content of quercetin 3-(6-malonylglucoside).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf403136wDOI Listing
September 2013

Anti-allergic effect of the flavonoid myricitrin from Myrica rubra leaf extracts in vitro and in vivo.

Nat Prod Res 2011 Feb;25(4):374-80

Department of Cooperative Medical Research, Collaboration Center, Shimane University, Izumo, Japan.

Flavonoids are ingested by the general population as anti-oxidant and anti-inflammatory agents. In this study, we investigated the effects of myricitrin, a flavonoid rich in Myrica rubra leaf, upon anti-inflammatory action. Myrica rubra leaf extracts inhibited pro-inflammatory TNFα production in a macrophage cell line, Raw264.7 cells. We observed that the serum IgE levels in the leaf extract-treated DO11.10, a mouse allergy model, were down-regulated. HPLC was performed to demonstrate that M. rubra leaf extracts contain a large amount of myricitrin. We observed an inhibitory effect of HPLC-purified myricitrin on TNFα production in Raw264.7 cells. Thus, myricitrin may be of potential interest in the management of inflammatory conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/14786411003774320DOI Listing
February 2011

Involvement of negative feedback regulation in wound-induced ethylene synthesis in 'Saijo' persimmon.

J Agric Food Chem 2006 Aug;54(16):5875-9

The United Graduate School of Agricultural Sciences, Tottori University, Japan.

Wounding is one of the most effective stress signals to induce ethylene synthesis in persimmon (Diospyros kaki Thunb.). We found that wound-induced ethylene biosynthesis is subjected to negative feedback regulation in mature 'Saijo' persimmon fruit since ethylene production was enhanced by 1-methylcyclopropene (1-MCP) (an inhibitor of ethylene perception) pretreatment, which was approximately 1.8 fold of that in control tissues (without 1-MCP pretreatment). Wound-induced 1-aminocyclopropane-1-carboxylate (ACC) synthase activity and DK-ACS2 gene expression were substantially increased by 1-MCP pretreatment after 12 h, which resulted in much higher ACC content in 1-MCP pretreated tissues than that in a control after 24 h. These results indicated that wound-induced DK-ACS2 gene expression was negatively regulated by ethylene in mature persimmon fruit. However, 1-MCP pretreatment had no effect on DK-ACO1 gene expression, suggesting the independence of wound-induced DK-ACO1 on ethylene. Out of accord with DK-ACO1 gene expression, ACC oxidase activity was enhanced 48 h after wounding in 1-MCP pretreated tissues, reaching a peak 1.5-fold higher than that in control tissues at 60 h.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jf060048hDOI Listing
August 2006

Ty1-copia group retrotransposons in persimmon (Diospyros kaki Thunb.).

Genes Genet Syst 2002 Apr;77(2):131-6

Faculty of Life and Environmental Sciences, Shimane University, Japan.

We cloned and characterized Ty1-copia group retrotransposons in persimmon (Diospyros kaki Thunb.). Genomic DNA or methyl jasmonate (MJA)-treated cDNA were used as templates to amplify the reverse transcriptase region of Ty1-copia group retrotransposons. About 280 bp fragments were amplified and cloned, and 97 clones were sequenced. Forty-nine clones included frameshift or the stop codon, or both. Among 48 clones containing complete reading frames, 42 clones had unique nucleotide sequences. Alignment and phylogenetic analysis of putative amino acid sequences in the 42 clones indicated that these clones (named Tdk; retroTransposon in Diospyros kaki) fell into seven subgroups and six ungrouped sequences, indicating high sequence heterogeneity in Tdk clones. Phylogenetic analysis comparing unrelated plant species shows that some Tdk clones are more closely related to Ty1-copia group retrotransposons in the orders Solanales and Sapindales rather than to other Tdk clones. Southern blot analysis using Tdk2B, Tdk4c, Tdk6Ac, Tdk12K and Tdk13G clones as probes showed that persimmon and its related species, D. lotus, D. lotus var. glabba, D. oleifera, D. rhombifolia and D. virginiana, contained multiple Tdk-like sequences, indicating that homologous elements exist in other Diospyros species.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1266/ggs.77.131DOI Listing
April 2002
-->