There are two glutamate dehydrogenases in the pathogenic fungus Candida albicans. One is an NAD+-dependent glutamate dehydrogenase (GDH2) and the other is an NADPH-dependent glutamate dehydrogenase (GDH3). These two enzymes are part of the nitrogen and nicotinate/nicotinamide metabolic pathways, which have been identified in our previous studies as potentially playing an important role in C. albicans morphogenesis. In this study, we created single gene knockout mutants of both dehydrogenases in order to investigate whether or not they affect the morphogenesis of C. albicans. The GDH genes were deleted and the phenotypes of the knockout mutants were studied by growth characterisation, metabolomics, isotope labelling experiments, and by quantifying cofactors under various hyphae-inducing conditions. We found that the gdh2/gdh2 mutant was unable to grow on either arginine or proline as a sole carbon and nitrogen source. While the gdh3/gdh3 mutant could grow on these carbon and nitrogen sources, the strain was locked in the yeast morphology in proline-containing medium. We detected different concentrations of ATP, NAD+, NADH, NAPD+, NADPH, as well as 62 other metabolites, and 19 isotopically labelled metabolites between the mutant and the wild-type strains. These differences were associated with 44 known metabolic pathways. It appears that the disequilibrium of cofactors in the gdh3/gdh3 mutant leads to characteristic proline degradation in the central carbon metabolism. The analysis of the gdh2/gdh2 and the gdh3/gdh3 mutants confirmed our hypothesis that redox potential and nitrogen metabolism are related to filament formation and identified these metabolic pathways as potential drug targets to inhibit morphogenesis.

中文翻译：

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代谢组学研究白色念珠菌谷氨酸脱氢酶缺失对生长和形态发生的影响。

致病真菌白色念珠菌中有两种谷氨酸脱氢酶。一种是NAD +依赖性谷氨酸脱氢酶（GDH2），另一种是NADPH依赖性谷氨酸脱氢酶（GDH3）。这两种酶是氮和烟酸/烟酰胺代谢途径的一部分，在我们先前的研究中已确定这两种途径可能在白色念珠菌的形态发生中发挥重要作用。在这项研究中，我们创建了两种脱氢酶的单基因敲除突变体，以研究它们是否影响白色念珠菌的形态发生。删除了GDH基因，并通过生长表征，代谢组学，同位素标记实验以及通过在各种诱导菌丝的条件下定量辅助因子来研究敲除突变体的表型。我们发现gdh2 / gdh2突变体无法在精氨酸或脯氨酸上作为唯一的碳和氮源生长。尽管gdh3 / gdh3突变体可以在这些碳源和氮源上生长，但该菌株却被锁定在含有脯氨酸的培养基中的酵母形态中。我们检测到不同浓度的ATP，NAD +，NADH，NAPD +，NADPH，以及突变体和野生型菌株之间的62种其他代谢物和19种同位素标记的代谢物。这些差异与44种已知的代谢途径有关。似乎gdh3 / gdh3突变体中辅因子的不平衡导致中央碳代谢中脯氨酸的特征降解。