Studies on the Mechanism of Action of Acetyl Coenzyme A Carboxylase

III. ENZYME-BOUND 1'-N-CARBOXYBIOTIN AS THE CARBOXYLATION INTERMEDIATE

From the ¹ From the Duke University Medical Center, Department of Biochemistry, Durham, North Carolina

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 acetyl- and 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 1'-N-methoxycarbonylbiotin methyl ester was isolated from the acetyl-CoA carboxylase substantiating the hypothesis that the 1'-N-carboxamide of enzyme-bound biotin is an intermediate in these carboxylation reactions.

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