Abstract

In mammalian tissues, propionyl CoA carboxylase and methylmalonyl CoA mutase act physiologically primarily in the ATP requiring direction of succinate formation. Therefore, propionate is glycogenic. However, many invertebrates and bacteria accumulate propionate from succinate. Employing acyl CoA transferase, propionyl CoA carboxylase, and methylmalonyl CoA mutase in the direction of propionate formation, substrate level ATP should be generated. The intestinal worm, Ascaris lumbricoides possesses mitochondria which function anaerobically and accumulate propionate and volatile fatty acids derived from propionate. Results of the present study indicate that a site of mitochondrial phosporylation may be present at the substrate level during the decarboxylation of succinate to propionate and C0 2. Mitochondrial preparations from Ascaris muscle exhibit propionyl CoA carboxylase, methylmalonyl CoA mutase, and acyl CoA transferase activities. Inorganic 32P is esterified during succinate decarboxylation. In accord with the proposed reactions, both succinate decarboxylation and 32P esterification are stimulated six- to eightfold upon the addition of propionyl CoA, and both stimulations are inhibited by avidin.

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