The Alcohol Dehydrogenase Gene adhA in Corynebacterium glutamicum Is Subject to Carbon Catabolite Repression

Abstract

Corynebacterium glutamicum has recently been shown to grow on ethanol as a carbon and energy source and to possess high alcohol dehydrogenase (ADH) activity when growing on this substrate and low ADH activity when growing on ethanol plus glucose or glucose alone. Here we identify the C. glutamicum ADH gene (adhA), analyze its transcriptional organization, and investigate the relevance of the transcriptional regulators of acetate metabolism RamA and RamB for adhA expression. Sequence analysis of adhA predicts a polypeptide of 345 amino acids showing up to 57% identity with zinc-dependent ADH enzymes of group I. Inactivation of the chromosomal adhA gene led to the inability to grow on ethanol and to the absence of ADH activity, indicating that only a single ethanol-oxidizing ADH enzyme is present in C. glutamicum. Transcriptional analysis revealed that the C. glutamicum adhA gene is monocistronic and that its expression is repressed in the presence of glucose and of acetate in the growth medium, i.e., that adhA expression is subject to catabolite repression. Further analyses revealed that RamA and RamB directly bind to the adhA promoter region, that RamA is essential for the expression of adhA, and that RamB exerts a negative control on adhA expression in the presence of glucose or acetate in the growth medium. However, since the glucose-and acetate-dependent down-regulation of adhA expression was only partially released in a RamB-deficient mutant, there might be an additional regulator involved in the catabolite repression of adhA.

Effect of carbon source availability and growth phase on expression of Corynebacterium glutamicum genes involved in the tricarboxylic acid cycle and glyoxylate bypass

“…The regulation of C. glutamicum metabolism in the presence of various carbon sources clearly differs from that of E. coli or B. subtilis (Gerstmeir et al, 2003;Hayashi et al, 2002;Letek et al, 2006;Muffler et al, 2002). No direct evidence has been found of a CCR system in C. glutamicum (Bruckner & Titgemeyer, 2002;Gerstmeir et al, 2003;Han et al, 2007), although a CCR-like phenomenon has been reported from cells grown on medium containing glucose with either glutamate (Gerstmeir et al, 2003;Kramer et al, 1990;Kronemeyer et al, 1995) or ethanol (Arndt & Eikmanns, 2007;Kotrbova-Kozak et al, 2007). However, mechanisms of true induction and repression in the TCA cycle have not been studied in depth.…”

Involvement of Regulatory Interactions among Global Regulators GlxR, SugR, and RamA in Expression of ramA in Corynebacterium glutamicum

“…Besides, no HPr kinase/phosphatase system is found in the C. glutamicum genome. These differences in the molecular characteristics are likely reflected in the capacity of C. glutamicum to cometabolize glucose and a variety of carbon sources, including sugars, organic acids, and aromatic compounds without catabolite repression (17)(18)(19)(20)(21)(22)(23)(24), expect for a few cases (25)(26)(27).…”

Arabitol Metabolism of Corynebacterium glutamicum and Its Regulation by AtlR

“…The organism can use a variety of sugars (e.g., glucose, fructose, sucrose, ribose, or maltose) and organic acids (acetate, propionate, pyruvate, lactate, or citrate) as single or combined carbon and energy sources for growth and also for amino acid production. C. glutamicum is also able to use ethanol as a sole carbon and energy source, using alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) for NAD-dependent oxidations to acetate, which is then activated to acetyl coenzyme A (acetyl-CoA) and channeled into the citric acid and glyoxylate cycles (2,4,5,44). The ADH gene (adhA) of C. glutamicum has been shown to be subject to complex, carbon source-dependent regulation by the global transcriptional regulators RamA, RamB, and GlxR (2,6,43).…”