title: Enzymatic carboxylation of biotin: molecular and catalytic properties of a component enzyme of acetyl CoA carboxylase.
abstract: The biotin carboxylase component of acetyl CoA carboxylase has been purified approximately 2000 times from Escherichia coli. This protein, which catalyzes the carboxylation of free d-biotin, is free of the biotin-containing carboxyl carrier protein, is homogeneous by polyacrylamide gel electrophoresis and analytical ultracentrifugation, and has been crystallized. Biotin carboxylase, with a molecular weight of approximately 100,000, is composed of two 50,000-dalton subunits. The catalytic capacity of biotin carboxylase is markedly enhanced by ethanol (11 times at 15% v/v), and certain other organic solvents; this may mimic an effector-mediated response. The kinetic effect is exclusively on the maximal velocity of the reaction. Activation by ethanol is reversible and not accompanied by aggregation or disaggregation of the enzyme.
mesh_terms: D001710:Biotin / Q000378:metabolism*; D002247:Carbon Isotopes; D002384:Catalysis; D003065:Coenzyme A; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology; D000431:Ethanol / Q000494:pharmacology; D007700:Kinetics; D008025:Ligases / Q000302:isolation & purification*
chemical_list: D002247:Carbon Isotopes; D000431:Ethanol; D001710:Biotin; D008025:Ligases; D003065:Coenzyme A