TCA Cycle and Glyoxylate Shunt of Corynebacterium glutamicum

The enzymes of the tricarboxylic acid (TCA) and glyoxylate cycles of Corynebacterium glutamicum and in particular their regulation have been intensively studied in the past years. Nearly all TCA and glyoxylate cycle genes are subject to growth phase- or carbon source-dependent transcriptional regulation. Seven different regulators were shown to be involved in expression control of TCA and glyoxylate cycle genes, i.e., AcnR, DtxR, GlxR, RamA, RamB, RipA, and SucR. At the level of enzyme activity, the 2-oxoglutarate dehydrogenase (ODH) complex was found to be controlled by the inhibitor protein OdhI in dependency of its phosphorylation state, which is determined by the serine/threonine protein kinases PknG, PknA, PknB, and PknL and by the phospho-serine/threonine protein phosphatase Ppp. OdhI was shown to be crucial for glutamate production. This chapter summarizes new data on TCA cycle enzymes and describes the current knowledge on the regulation of this pathway and of the glyoxylate shunt