The Utilization of Propionate by Micrococcus denitrificans

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Abstract
Surmmary Suspensions of Micrococcus denitrificans, growing with propionate as sole carbon source, incorporated 14C from [1-14C]propionate or from sodium [14C]bicarbonate, initially into succinate and then into intermediates of the tricarboxylic acid cycle and amino acids derived therefrom. In the presence of 4 mM-sodium arsenite, the oxidation of propionate and of L-malate by washed organisms proceeded only to the level of pyruvate, which accumulated: when sodium [14C]bicarbonate was also present, the pyruvate formed from propionate, but not that formed from L-malate, was highly radioactive. Cell-free extracts of propionate-grown M. denitrificans catalysed the formation of labelled methylmalonyl-coenzyme A, succinyl-coenzyme A and succinate from sodium [14C]carbonate+ ATP + either propionate and coenzyme A, or propionyl-coenzyme A. The evidence thus obtained indicates that propionate enters the tricarboxylic acid cycle of M. denitrificans, preponderantly via activation to propionyl-coenzyme A, followed by carboxylation to methyl-malonyl coenzyme A, isomerization to succinyl-coenzyme A and hydrolysis to succinate.

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