TRANSCARBOXYLASE, II. PURIFICATION AND PROPERTIES OF METHYLMALONYL-OXALOACETIC TRANSCARBOXYLASE

Publisher Website
Google Scholar
Abstract
The enzyme system which catalyzes the reversible transfer of carboxyl groups from methylmalonyl CoA to pyruvate to form oxaloacetate and propionyl CoA has been purified from propionibacteria. The reaction is probably catalyzed by a single enzyme which is referred to as methylmalonyl-oxaloacetic transcarboxylase. The enzyme may contain biotin, since it is inhibited by avidin. No added cofactors are required for the reaction. The enzyme has a broad specificity for the CoA component. With oxaloacetate as the carboxyl donor acetyl CoA, propionyl CoA, butyryl CoA, or acetoacetyl CoA will serve as acceptor. The specificity for the keto acid component is narrow. Pyruvate was the only keto acid found capable of acting as a carboxyl acceptor from methylmalonyl CoA. The equilibrium constant of the reaction was found to be 1.9 at pH 6.5 and 30[degree] and the AF[degree]303 is calculated to be -3.9 x 102 calories. The possible role of transcarboxylase in promoting synthesis by transferring carboxyl groups between different pathways of metabolism is discussed.