Anti-Factor XIII, subunit A

Factor XIII (F.XIII, fibrin stabilizing factor) is the proenzyme form of a transamidase that is essential for normal haemostasis and , fibrinolysis, wound healing, female fertility and foetal development. Extracellular F.XIII consists of A subunits (83kD each) which contain the enzyme moiety, and B subunits (76kD each) which act as a carrier protein for the A subunit in circulation. Both subunits are produced under separate genetic control. In plasma, F.XIII exists as a non-covalent tetrameric complex (320kD) of two A-subunits and two B-subunits (A2B2). The concentration of F.XIII tetramer in plasma is ~25ug/ml (~80nM). An intracellular form of F.XIII is found in platelets, megakaryocytes and monocytes. This form of F.XIII presents as a dimer of two A-subunits only and has a molecular weight of 160kD. The importance of these intracellular stores is demonstrated by the observation that platelets can contribute up to half of the F.XIII activity in platelet rich plasma. The activation of F.XIII involves several steps. Thrombin cleaves after Arg37 of each A- subunit in the A2B2 tetramer, releasing a 4.5kD activation peptide. Additional conformational changes induced by the binding of calcium, and by dissociation of the B-subunits from the A-subunit dimer are required to obtain full enzyme activity. F.XIIIa is a cysteine protease that catalyses the formation of gamma-glutamyl-epsilon-lysyl bonds between the gamma and alpha chains of polymerised fibrin molecules. Other proteins found crosslinked into fibrin clots by F.XIIIa include fibrinogen, alpha 2 antiplasmin, fibronectin, vitronectin and von Willebrand factor. Applications: Suitable for use in ELISA and Immunoelectrophoresis. Other applications not tested. Recommended Dilution: Optimal dilutions to be determined by the researcher. Storage and Stability: May be stored at 4°C for short-term only. For long-term storage, aliquot and store at -20°C. Aliquots are stable for at least 12 months at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.