title: Vitamin K-dependent carboxylase. Control of enzyme activity by the "propeptide" region of factor X.
abstract: A liver microsomal enzyme catalyzes the vitamin K-dependent posttranslational carboxylation of specific glutamyl residues of a limited number of plasma proteins to gamma-carboxyglutamyl residues. The intracellular precursor forms of these proteins are known to contain a homologous basic amino acid-rich propeptide region between the signal peptide region and the amino terminus of the mature protein. This region of the precursor protein has been implicated as a possible recognition site for the carboxylase enzyme. A 20-residue peptide containing the octadecapropeptide of human clotting factor X has now been shown to strongly stimulate the activity of the enzyme toward a noncovalently linked substrate. This stimulatory effect is seen at less than micromolar concentrations and is accompanied by a decrease in the Km of the glutamic acid substrate. These observations raise the possibility that the catalytic activity of other enzymes involved in protein processing may be regulated by a portion of their normal substrates.
mesh_terms: D000818:Animals; D019735:Carbon-Carbon Ligases; D002851:Chromatography, High Pressure Liquid; D005170:Factor X / Q000378:metabolism*; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D007700:Kinetics; D008025:Ligases / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology*; D011499:Protein Processing, Post-Translational; D051381:Rats
chemical_list: D005971:Glutamates; D018698:Glutamic Acid; D005170:Factor X; D008025:Ligases; D019735:Carbon-Carbon Ligases; C020660:glutamyl carboxylase