title: Inactivation of human blood coagulation factor X by chemical modification of gamma-carboxyglutamic acid residues.
abstract: The inactivation of human factor X by incubation with a reagent known to chemically modify gamma-carboxyglutamic acid to gamma-methylene glutamic acid was studied. Incubation of factor X at pH 5.0 with a preincubated formaldehyde/morpholine mixture (0.9 M/1.0 M) resulted in a progressive decrease in factor X coagulant activity. In the presence of calcium (20 mM) the rate of factor X inactivation was decreased -3-fold. By using [14]C-formaldehyde, modified-factor X (less than 5% residual activity) was found to contain 7 mols of [14]C per mol of protein. Modified-factor X was not activated by Russell's viper venom in the presence of calcium, suggesting that the loss of coagulant activity was related to the inability of modified-factor X to be activated.
mesh_terms: D015055:1-Carboxyglutamic Acid / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002250:Carbon Radioisotopes; D005170:Factor X / Q000037:antagonists & inhibitors*; D005557:Formaldehyde / Q000494:pharmacology; D005971:Glutamates / Q000378:metabolism*; D006801:Humans; D007700:Kinetics
chemical_list: D002250:Carbon Radioisotopes; D005971:Glutamates; D005557:Formaldehyde; D015055:1-Carboxyglutamic Acid; D005170:Factor X; D002118:Calcium