Pathways in the activation of human coagulation factor X.
Purified human Factor X (apparent mol.wt. 72000), which consists of two polypeptide chains (mol.wt. 55000 and 19000), was activated by both Russell's-viper venom and the purified physiological activators (Factor VII/tissue factor and Factor IXa/Factor VIII). They all convert Factor X to catalytically active Factor Xa (mol.wt. 54000) by cleaving the heavy chain at a site on the N-terminal region. In the presence of Ca2+ and phospholipid, the Factor Xa formed catalyses (a) the cleavage of a small peptide (mol.wt. 4000) from the C-terminal region of the heavy chain of Factor Xa, resulting in a second active form (mol.wt. 50000), and (b) the cleavage of a peptide containing the active-site serine residue (mol.wt. 13000) from the C-terminal region of the heavy chain of Factor X, resulting in an inactivatable component (mol.wt. 59000). A nomenclature for the various products is proposed.
D001665:Binding Sites; D055598:Chemical Phenomena; D002621:Chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D005164:Factor IX / Q000494:pharmacology; D005167:Factor VII / Q000494:pharmacology; D005169:Factor VIII / Q000494:pharmacology; D005170:Factor X / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D010743:Phospholipids / Q000378:metabolism; D014757:Viper Venoms / Q000494:pharmacology
D010743:Phospholipids; D014757:Viper Venoms; D005167:Factor VII; D005169:Factor VIII; D005164:Factor IX; D005170:Factor X