The<unk> s,<unk>  A <unk> A) and<unk>  B <unk> B), are peptides which are located in the central region of the fibrous glycoprotein fibrinogen (factor I) and are cleaved by the enzyme thrombin (factor IIa) to convert fibrinogen into covalently-linked fibrin (factor IA) monomers. The N-terminal<unk> A is cleaved from the Aα chains of fibrinogen and<unk> B from the Bβ chains of fibrinogen, with<unk> A released before<unk> B. Subsequent to their formation, fibrin monomers are converted to cross-linked fibrin polymers by the action of thrombin-activated factor XIII (fibrin stabilizing factor), and these fibrin polymers form the backbone of a thrombus (blood clot). Hence, the<unk> s are sensitive markers of fibrinogenesis (fibrin generation), thrombin activity, and coagulation.<unk> A is a 16-amino acid peptide. The half-life of<unk> A is very short at approximately 3 to 5 minutes. Hence,<unk> A levels provide a relatively transient measure of coagulation activation. Levels of<unk> A increase with age.<unk> A levels also gradually increase throughout pregnancy. Likewise,<unk> A levels have been reported to increase with estrogen therapy, including with combined birth control pills and menopausal hormone therapy, although research on<unk> A levels with these therapies appears to be relatively limited.
Fibrinopeptide
Fibrinogen
Fibrin degradation product
Kallikrein
Β-Thromboglobulin
Von Willebrand factor
Fibrin monomer
Platelet-activating factor