title: Vitamin K-dependent carboxylase. Solubilization and properties.
abstract: Vitamin K is required for an enzymatic carboxylation of glutamyl residues in a microsomal protein precursor of plasma prothrombin to form gamma-carboxyglutamic acid. The enzyme system (carboxylase) which catalyzes this reaction has now been solubilized by extraction of the microsomes with Triton X-100 and has been shown to fix H14CO3- as gamma-carboxyglutamic acid residues in biologically active prothrombin. Enzyme activity requires O2 and vitamin K hydroquinone or vitamin K + NADH. Unlike the microsomal-bound carboxylase, soluble carboxylase activity is independent of either ATP or Mg2+ addition and is unaffected by either the ATP analog, adenyl-5'-yl imidodiphosphate (AMP-P(NH)P, or EDTA. These observations suggest that the energy required to drive the carboxylation reaction is derived from the oxidation of the reduced form of vitamin K. Although the membrane-bound carboxylase is inhibited by Warfarin, this anticoagulant is ineffective as an inhibitor of the soluble enzyme. A second anticoagulant, 2-chloro-3-phytyl-1,4-natpthoquinone (chloro-K), differs from Warfarin in that it effectively inhibits both the membrane-bound and soluble carboxylases.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002262:Carboxy-Lyases / Q000302:isolation & purification / Q000378:metabolism*; D004789:Enzyme Activation; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D010101:Oxygen Consumption; D011092:Polyethylene Glycols; D011516:Prothrombin / Q000378:metabolism; D051381:Rats; D012995:Solubility; D014812:Vitamin K / Q000031:analogs & derivatives / Q000494:pharmacology*; D014813:Vitamin K Deficiency / Q000201:enzymology; D014859:Warfarin / Q000494:pharmacology
chemical_list: D014812:Vitamin K; D011092:Polyethylene Glycols; D014859:Warfarin; D000255:Adenosine Triphosphate; D011516:Prothrombin; D002262:Carboxy-Lyases; D008274:Magnesium