Lin, Yuping He, Peng Wang, Qinhong Lu, Dajun Li, Zilong Wu, Changsheng Jiang, Ning The Alcohol Dehydrogenase System in the Xylose-Fermenting Yeast <em>Candida maltosa</em> <div><h3>Background</h3><p>The alcohol dehydrogenase (ADH) system plays a critical role in sugar metabolism involving in not only ethanol formation and consumption but also the general “cofactor balance” mechanism. <em>Candida maltosa</em> is able to ferment glucose as well as xylose to produce a significant amount of ethanol. Here we report the ADH system in <em>C. maltosa</em> composed of three microbial group I ADH genes (<em>CmADH1</em>, <em>CmADH2A</em> and <em>CmADH2B</em>), mainly focusing on its metabolic regulation and physiological function.</p><h3>Methodology/Principal Findings</h3><p>Genetic analysis indicated that <em>CmADH2A</em> and <em>CmADH2B</em> tandemly located on the chromosome could be derived from tandem gene duplication. <em>In vitro</em> characterization of enzymatic properties revealed that all the three CmADHs had broad substrate specificities. Homo- and heterotetramers of CmADH1 and CmADH2A were demonstrated by zymogram analysis, and their expression profiles and physiological functions were different with respect to carbon sources and growth phases. Fermentation studies of ADH2A-deficient mutant showed that <em>CmADH2A</em> was directly related to NAD regeneration during xylose metabolism since CmADH2A deficiency resulted in a significant accumulation of glycerol.</p><h3>Conclusions/Significance</h3><p>Our results revealed that <em>CmADH1</em> was responsible for ethanol formation during glucose metabolism, whereas <em>CmADH2A</em> was glucose-repressed and functioned to convert the accumulated ethanol to acetaldehyde. To our knowledge, this is the first demonstration of function separation and glucose repression of ADH genes in xylose-fermenting yeasts. On the other hand, <em>CmADH1</em> and <em>CmADH2A</em> were both involved in ethanol formation with NAD regeneration to maintain NADH/NAD ratio in favor of producing xylitol from xylose. In contrast, <em>CmADH2B</em> was expressed at a much lower level than the other two CmADH genes, and its function is to be further confirmed.</p></div> dehydrogenase;xylose-fermenting;yeast 2010-07-23
    https://plos.figshare.com/articles/dataset/The_Alcohol_Dehydrogenase_System_in_the_Xylose_Fermenting_Yeast_Candida_maltosa_/142525
10.1371/journal.pone.0011752