Factor XIII (both A & B subunits), human
Factor XIII (A subunit only), human
Description of Factor XIII (FXIII)
Factor XIII (FXIII, 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 (83 kDa each) which contain the enzyme moiety, and B subunits (76 kDa each) which act as a carrier protein for the A subunit in circulation. Both subunits are produced under separate genetic control. In plasma, FXIII exists as a non-covalent tetrameric complex (320 kDa) of two A-subunits and two B-subunits (A2B2). The concentration of F.XIII tetramer in plasma is ~25 Î¼g/ml (~80 nM). An intracellular form of FXIII 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 160 kDa. The importance of these intracellular stores is demonstrated by the observation that platelets can contribute up to half of the FXIII activity in platelet rich plasma. The activation of FXIII involves several steps. Thrombin cleaves after Arg37 of each A-subunit in the A2B2 tetramer, releasing a 4.5 kDa 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. FXIIIa is a cysteine protease that catalyses the formation of Î³-glutamyl-Îµ-lysyl bonds between the Î³ and Î± chains of polymerised fibrin molecules. Other proteins found crosslinked into fibrin clots by FXIIIa include fibrinogen, Î±2antiplasmin, fibronectin, vitronectin and von Willebrand factor 1-3.
1. McDonagh J; Structure and Function of Factor XIII; in Hemostasis and Thrombosis, 3rd Edition, eds. RW Colman, J Hirsh, VJ Marder and EW Salzman, pp 301-313, J.B. Lippincott Co., Philadelphia PA, USA, 1994.
2. Inbal A, Muszbek L; Coagulation Factor Deficiencies and Pregnancy Loss; Seminars in Thrombosis and Haemostasis 29, pp 171-174, 2003.
3. Murdock PJ, Owens DL, Chitolie A, Hutton RA, Lee CA; Development and Evaluation of ELISAs for Factor XIIIA and XIIIB Subunits in Plasma; Thrombosis Research 67, pp 73-79, 1992.
SAFXIII-HRP Sheep anti-human Factor XIII, peroxidase labelled IgG
SAF13A-IG Sheep anti-F.XIII-subunit A, whole IgG from antiserum
SAF13A-AP Sheep anti-F.XIII-subunit A, affinity purified IgG
SAF13A-HRP Sheep anti-F.XIII-subunit A, peroxidase labelled IgG
FXIII-EIA Paired antibody set for ELISA of F.XIII, 5 x 96 wells