The reaction mechanisms and substrate-stereospecificities of L-alloisocitrate dehydrogenase and oxalosuccinate decarboxylase.
A sequential reaction was suggested for the conversion of L-alloisocitrate to alpha-oxoglutarate by an enzyme complex of L-alloisocitrate dehydrogenase and oxalosuccinate decarboxylase from Pseudomonas strain No. 2, during which oxalosuccinate was not released from the enzyme-substrate complex. The stereochemistry of oxalosuccinate formed by L-alloisocitrate dehydrogenase and decarboxylated by oxalosuccinate decarboxylase was opposite to that of the substrate for D-isocitrate dehydrogenase. Incubation of L-alloisocitrate with the dehydrogenase and decarboxylase in deuterium oxide provided [3-2H]-alpha-oxoglutarate, the configuration of which turned out to be the same as that produced by D-isocitrate dehydrogenase from D-isocitrate. The data suggested that enol form of alpha-oxoglutarate was involved as an intermediate in decarboxylation of oxalosuccinate by oxalosuccinate decarboxylase. L-Alloisocitrate dehydrogenase was shown to react with pro-S proton of NADH.
D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007523:Isocitrates / Q000378:metabolism; D007700:Kinetics; D011549:Pseudomonas / Q000201:enzymology; D013237:Stereoisomerism; D013379:Substrate Specificity
D007523:Isocitrates; C034219:isocitric acid; D000429:Alcohol Oxidoreductases; C026047:alloisocitrate dehydrogenase; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+)