title: Factor V.
abstract: Factor V is a single chain glycoprotein that plays an essential role in the regulation of blood coagulation. After initiation of coagulation, factor V is converted into factor Va through limited proteolysis. Factor Va acts as protein cofactor in the prothrombin-activating complex, which is comprised of the serine protease factor Xa, Ca2+ ions and a procoagulant membrane surface. Factor Va accelerates factor Xa-catalysed conversion of prothrombin into thrombin more than 10(4)-fold. The cofactor activity of factor Va in prothrombin activation is down-regulated by activated protein C (APC). The physiological importance of this regulatory pathway is demonstrated by the occurrence of hereditary thrombophilia in individuals with a genetic defect that makes factor Va less sensitive to proteolytic inactivation by APC (APC resistance).
authors.affiliation: Department of Biochemistry, Maastricht University, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Rosing
authors.forename: G
authors.initials: G
authors.lastname: Tans
mesh_terms: D001777:Blood Coagulation / Q000502:physiology*; D005165:Factor V / Q000737:chemistry / Q000502:physiology*; D015943:Factor Va / Q000502:physiology*; D006801:Humans; D011516:Prothrombin / Q000378:metabolism; D013917:Thrombin / Q000096:biosynthesis
chemical_list: D015943:Factor Va; D005165:Factor V; D011516:Prothrombin; D013917:Thrombin