Biotin and the Formation of Carboxyl Groups from Bicarbonate

C. Biotin and the Formation of Carboxyl Groups from Bicarbonate 728 Box 14-B The Biotin-Binding Proteins Avidin and Streptavidin... 

C. Biotin and the Formation of Carboxyl Groups from Bicarbonate... 

The formation of a bond between the carboxylate group derived from bicarbonate and a carbon adjacent to a carbonyl group is indicative of a reaction catalyzed by an enzyme that utilizes biotin as a cofactor (Scheme 16). The recent review by Knowles covers many recent discoveries relating to the role of enzymes in these reactions (43). (Editor s note For additional aspects of biotin-dependent carboxylation, see Chapter 6 by O Leary.) Most biotin-dependent enzymes promote a two-step process in which Ai-carboxybiotin serves as an intermediate in a process involving the exchange of the caiix)xylate group derived from bicarbonate for a proton at the a-carbon of the carbonyl compound (44). 

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