title: A role of the transcriptional regulator LldR (NCgl2814) in glutamate metabolism under biotin-limited conditions in Corynebacterium glutamicum.
abstract: Corynebacterium glutamicum is a Gram-positive, rod-shaped, aerobic bacterium used for the fermentative production of L-glutamate. LldR (NCgl2814) is known as a repressor for ldhA and lldD encoding lactate dehydrogenases. LdhA is responsible for production of L-lactate, while LldD is for its assimilation. Since L-lactate production was observed as a by-product of glutamate production under biotin-limited conditions, LldR might play a regulatory role in the glutamate metabolism. Here for the first time, we investigated effects of overproduction or deletion of LldR on the glutamate metabolism under biotin-limited conditions in C. glutamicum. It was found that glutamate production under biotin-limited conditions was decreased by overproduction of LldR. In the wild-type cells, L-lactate was produced in the first 24 h and it was re-consumed thereafter. On the other hand, in the overproduced cells, L-lactate was produced like the wild type, but it was not re-consumed. This means that L-lactate assimilation, which is catalyzed by LldD, was suppressed by the overproduction of LldR, but L-lactate production, which is catalyzed by LdhA, was not affected, indicating that LldR mainly controls the expression of lldD but not of ldhA under biotin-limited conditions. This was confirmed by quantitative real-time RT-PCR. From these results, it is suggested that L-lactate metabolism, which is controlled by LldR, has a buffering function of the pyruvate pool for glutamate production.
authors.affiliation: Department of Bioengineering, Tokyo Institute of Technology, Japan.
authors.forename: Tanyanut
authors.initials: T
authors.lastname: Supkulsutra
authors.forename: Tomoya
authors.initials: T
authors.lastname: Maeda
authors.forename: Kosuke
authors.initials: K
authors.lastname: Kumagai
authors.forename: Masaaki
authors.initials: M
authors.lastname: Wachi
mesh_terms: D001710:Biotin / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D018698:Glutamic Acid / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D012097:Repressor Proteins; D019344:Lactic Acid; D018698:Glutamic Acid; D001710:Biotin; D007770:L-Lactate Dehydrogenase