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

Abstract
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.