Normandie Univ, UNICAEN U2RM-Stress and Virulence, Esplanade de la Paix, 14032 Caen, France.
Dipartimento di Scienze di Laboratorio e Infettivologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, Largo A. Gemelli 8, 00168 Rome, Italy.
FEMS Microbiol Lett. 2021 May 6;368(8). doi: 10.1093/femsle/fnab043.
Glycerol (Gly) can be dissimilated by two pathways in bacteria. Either this sugar alcohol is first oxidized to dihydroxyacetone (DHA) and then phosphorylated or it is first phosphorylated to glycerol-3-phosphate (GlyP) followed by oxidation. Oxidation of GlyP can be achieved by NAD-dependent dehydrogenases or by a GlyP oxidase. In both cases, dihydroxyacetone phosphate is the product. Genomic analysis showed that Enterococcus faecium harbors numerous genes annotated to encode activities for the two pathways. However, our physiological analyses of growth on glycerol showed that dissimilation is limited to aerobic conditions and that despite the presence of genes encoding presumed GlyP dehydrogenases, the GlyP oxidase is essential in this process. Although E. faecium contains an operon encoding the phosphotransfer protein DhaM and DHA kinase, which are required for DHA phosphorylation, it is unable to grow on DHA. This operon is highly expressed in stationary phase but its physiological role remains unknown. Finally, data obtained from sequencing of a transposon mutant bank of E. faecium grown on BHI revealed that the GlyP dehydrogenases and a major intrinsic family protein have important but hitherto unknown physiological functions.
甘油（Gly）可以通过细菌中的两种途径进行异化。这种糖醇要么先被氧化为二羟丙酮（DHA），然后再磷酸化，要么先被磷酸化为甘油-3-磷酸（GlyP），然后再氧化。GlyP 的氧化可以通过 NAD 依赖性脱氢酶或 GlyP 氧化酶来实现。在这两种情况下，产物都是二羟丙酮磷酸。基因组分析表明，屎肠球菌（Enterococcus faecium）拥有许多基因，这些基因被注释为编码两条途径的活性。然而，我们对甘油生长的生理分析表明，异化仅限于需氧条件，尽管存在编码假定的 GlyP 脱氢酶的基因，但 GlyP 氧化酶在这个过程中是必不可少的。尽管屎肠球菌含有一个操纵子，编码 DhaM 和 DHA 激酶的磷酸转移蛋白，这是 DHA 磷酸化所必需的，但它不能在 DHA 上生长。该操纵子在静止期高度表达，但生理作用仍不清楚。最后，从 BHI 上生长的屎肠球菌转座子突变体库的测序中获得的数据表明，GlyP 脱氢酶和一种主要的内在家族蛋白具有重要但迄今未知的生理功能。
