Studies on the mechanism of action of acetyl coenzyme A carboxylase. I. Effect of isocitrate on the transcarboxylation step of acetyl coenzyme A carboxylase.

Studies presented here, with the criterion of the degree of binding of the biotin derivatives obtained from acetyl coenzyme A carboxylase to avidin, show that these compounds have an intact ureido ring, eliminating the diamine derivative as an intermediate in the carboxylation. With the use of carboxyl-14C-biotin acetyland propionyl-CoA carboxylases, it has been possible to show both in vivo and in vitro that no turnover of the ureido carbon of biotin occurs in the carboxylation reaction. The l’-N-methoxycarbonylbiotin methyl ester was isolated from the acetyl-CoA carboxylase substantiating the hypothesis that the l’-N-carboxamide of enzyme-bound biotin is an intermediate in these carboxylation reactions.