Vitamin K-dependent carboxylase. Stoichiometry of carboxylation and vitamin K 2,3-epoxide formation.
Crude rat liver microsomal preparations catalyze a reduced vitamin K- and oxygen-dependent carboxylation of peptide-bound glutamyl residues to gamma-carboxyglutamyl residues. The same preparations convert reduced vitamin K to its 2,3-epoxide. The stoichiometry of this relationship has been investigated. At saturating concentrations of CO2, equal amounts of vitamin K 2,3-epoxide and gamma-carboxyglutamic acid are formed. As the CO2 concentration is lowered, this ratio shifts to a large excess of epoxide. Alterations in glutamyl substrate concentration or Mn2+ concentration cause equal alterations in both activities, while addition of KCN stimulated epoxidation and inhibited carboxylation. The release of 3H from a gamma-[3H]glutamyl substrate was tightly coupled to epoxide formation, and both of these activities were inhibited by glutathione peroxidase. These data are consistent with a reaction mechanism in which an oxygenated form of vitamin K activates the substrate glutamyl residue by hydrogen removal in a reaction that is coupled to vitamin K epoxide formation.
D000818:Animals; D019735:Carbon-Carbon Ligases; D002712:Chlorides; D007700:Kinetics; D008025:Ligases / Q000378:metabolism*; D008345:Manganese / Q000494:pharmacology; D017895:Manganese Compounds; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D011190:Potassium Cyanide / Q000494:pharmacology; D051381:Rats; D014812:Vitamin K / Q000031:analogs & derivatives* / Q000378:metabolism*; D024482:Vitamin K 2 / Q000031:analogs & derivatives*; D014813:Vitamin K Deficiency / Q000201:enzymology; D064417:Vitamin K Epoxide Reductases
C024854:2,3-epoxymenaquinone; D002712:Chlorides; D017895:Manganese Compounds; D024482:Vitamin K 2; D014812:Vitamin K; D008345:Manganese; D006899:Mixed Function Oxygenases; D064417:Vitamin K Epoxide Reductases; D008025:Ligases; D019735:Carbon-Carbon Ligases; C020660:glutamyl carboxylase; D011190:Potassium Cyanide; C025340:manganese chloride