ACETYL COA CARBOXYLASE, II. DEMONSTRATION OF BIOTIN-PROTEIN AND BIOTIN CARBOXYLASE SUBUNITS

Previous work has shown that Escherichia coli acetyl CoA carboxylase is composed of two dissimilar protein components, E(a) which contains covalently bound biotin and forms E(a)-CO(2)-from HCO(3)- and ATP, and E(b) which is involved in the transfer of the carboxyl group from E(a)-CO(2)- to acetyl CoA, forming malonyl CoA. E(a) has been dissociated into two subunits at pH 9. One subunit, designated biotin carboxylase, catalyzes a model reaction, the ATP-dependent carboxylation of free (+)-biotin. The other subunit contains covalently bound which is carboxylated by the biotin carboxylase in the course of acetyl CoA carboxylation.