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Evidence for oxidative thiolytic cleavage of acetoin in Pelobacter carbinolicus analogous to aerobic oxidative decarboxylation of pyruvate

1989; Oxford University Press; Volume: 60; Issue: 1 Linguagem: Inglês

10.1111/j.1574-6968.1989.tb03429.x

1574-6968

Fred Bernd Oppermann, Alexander Steinbà ⁄ chel, Hans G. Schlegel,

Polyamine Metabolism and Applications

Dihydrolipoamide dehydrogenase and dihydrolipoamide acetyltransferase were formed when Pelobacter carbinolicus strain GraBd1 was grown on acetoin. The specific activities of these enzymes amounted to 0.50 and 28.7 U/mg protein, respectively. The crude extract catalyzed the CoASH-and NAD+-dependent formation of acetyl-CoA from acetoin and methylacetoin. From ethylene glycol-grown cells these activities were absent. Crude extracts also exhibited acetoin: methyl viologen and acetoin: metronidazol oxidoreductase activity. As shown by reconstitution experiments methylviologen reduction was dependent on the presence of a light-brownish protein (Mr 220 000 ± 10 000); metronidazol reduction was in addition dependent on the presence of a dark-brownish protein (Mr 4 900 ± 800), which is probably a ferredoxin. However, both components were synthesized constitutively. We discussed a model for oxidative-thiolytic cleavage of acetoin which is analogous to the reaction of the pyruvate dehydrogenase enzyme complex rather than to pyruvate: ferredoxin oxidoreductase.