Structural-functional transformation of the malate dehydrogenase system of the bacterium <Emphasis Type="Italic">Sphaerotilus</Emphasis> sp. strain D-507 depending on nutritional mode

High-purity preparations of malate dehydrogenase (EC 1.1.1.37) were obtained by multistage purification from the bacterium Sphaerotilus sp. strain D-507 growing under different conditions. Under organotrophic conditions, the enzyme was dimeric; under mixotrophic conditions, dimeric and trimeric. On the basis of studied properties of the enzyme preparations, data on the activity of enzymes of the glyoxylate and tricarboxylic-acid cycles, and analysis of published data, it can be concluded that malate dehydrogenase isoforms are implicated in the adaptive response of bacteria to changing culturing conditions.