Hierarchy in pentose sugar metabolism in Clostridium acetobutylicum.

Authors:
Dr. Ludmilla Aristilde, PhD
Dr. Ludmilla Aristilde, PhD
Cornell University
Associate Professor
Environmental Chemistry; Environmental Biochemistry; Environmental Engineering.
Ithaca, NY | United States
Ian A Lewis
Ian A Lewis
University of Calgary
United States
Junyoung O Park
Junyoung O Park
Lewis-Sigler Institute for Integrative Genomics
Princeton | United States
Joshua D Rabinowitz
Joshua D Rabinowitz
Lewis-Sigler Institute for Integrative Genomics
United States

Appl Environ Microbiol 2015 Feb;81(4):1452-62

Bacterial metabolism of polysaccharides from plant detritus into acids and solvents is an essential component of the terrestrial carbon cycle. Understanding the underlying metabolic pathways can also contribute to improved production of biofuels. Using a metabolomics approach involving liquid chromatography-mass spectrometry, we investigated the metabolism of mixtures of the cellulosic hexose sugar (glucose) and hemicellulosic pentose sugars (xylose and arabinose) in the anaerobic soil bacterium Clostridium acetobutylicum. Simultaneous feeding of stable isotope-labeled glucose and unlabeled xylose or arabinose revealed that,as expected, glucose was preferentially used as the carbon source. Assimilated pentose sugars accumulated in pentose phosphate pathway (PPP) intermediates with minimal flux into glycolysis. Simultaneous feeding of xylose and arabinose revealed an unexpected hierarchy among the pentose sugars, with arabinose utilized preferentially over xylose. The phosphoketolase pathway (PKP) provides an alternative route of pentose catabolism in C. acetobutylicum that directly converts xylulose-5-phosphate into acetyl-phosphate and glyceraldehyde-3-phosphate, bypassing most of the PPP. When feeding the mixture of pentose sugars, the labeling patterns of lower glycolytic intermediates indicated more flux through the PKP than through the PPP and upper glycolysis, and this was confirmed by quantitative flux modeling. Consistent with direct acetyl-phosphate production from the PKP, growth on the pentose mixture resulted in enhanced acetate excretion. Taken collectively, these findings reveal two hierarchies in clostridial pentose metabolism: xylose is subordinate to arabinose, and the PPP is used less than the PKP.

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Source
http://dx.doi.org/10.1128/AEM.03199-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4309709PMC
February 2015
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