title: Acetyl coenzyme A carboxylase. Rapid purification of the chick liver enzyme and steady state kinetic analysis of the carboxylase-catalyzed reaction.
abstract: Avidin affinity chromatography was used to rapidly purify acetyl-CoA carboxylase to homogeneity in high yield from chicken liver. Dissociation of the purified carboxylase with dodecyl sulfate yielded a single size class of subunit polypeptide of 225,000 daltons. A steady state kinetic analysis of the carboxylase-catalyzed carboxylation of acetyl-CoA gave rise to intersecting line patterns in all double-reciprocal plots of initial velocity with each substrate pair, i.e. ATP . Mg and HCO3(-) and acetyl-CoA. It was concluded that the kinetic mechanism involves a quaternary complex of the enzyme, ADP, Pi, and acetyl-CoA rather than a double displacement as previously believed. The ordered addition of ATP, HCO3(-), and then acetyl-CoA, to the citrate-activated form of the carboxylase is the kinetic mechanism most consistent with the results.
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000302:isolation & purification* / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002645:Chickens; D007700:Kinetics; D008025:Ligases / Q000302:isolation & purification*; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D011485:Protein Binding
chemical_list: D001639:Bicarbonates; D008025:Ligases; D000103:Acetyl-CoA Carboxylase