[Role of malate dehydrogenase isoforms in the regulation of anabolic and catabolic processes in the colorless sulfur bacterium Beggiatoa leptomitiformis D-402].

The functional role of tetrameric and dimeric isoforms of malate dehydrogenase in the carbon metabolism of the colorless sulfur bacterium Beggiatoa leptomitiformis, strain D-402, was studied. This strain can grow both lithotrophically and organotrophically. By using the inhibition analysis, the tetrameric isoenzyme was shown to operate in the glyoxylate cycle and the dimeric one was found to be involved in the TCA cycle. The dynamics of the dimeric isoenzyme conversion to the tetrameric isoform was found to be determined by the rate of thiosulfate oxidation. The regulation of the carbon metabolism in Beggiatoa leptomitiformis is supposed to be accomplished by means of structural and functional changes in the protein molecule of malate dehydrogenase.