Factor XIII is the zymogenic form of the glutaminyl-peptide g-glutamyl transferase factor XIIIa (fibrinoligase, plasma transglutaminase, fibrin stabilizing factor, E.C. 2.3.2.13) (1-3). Factor XIII is unique among transamidases in that it is a zymogen in vivo (2). Factor XIII is found both extracellularly in plasma and intracellularly in platelets, megakaryocytes, monocytes, placenta, uterus, liver and prostrate tissues. Plasma factor XIII is synthesized in the liver and circulates as a tetramer (Mr 20,000), composed of 2 pairs of nonidentical subunits (A2B2) (4). The intracellular forms are synthesized in the tissues where they reside as dimers (Mr 6000) of 2 identical A chains (A2) (7-11). The A subunits of plasma and intracellular forms of factor XIII are functionally identical. The A subunit contains 6 free sulfhydryl groups one of which is the active site (12). The concentration of factor XIII in plasma (A2B2) is approximately 30mg/ml (8). It is the last of the zymogens to become activated in the coagulation cascade and it is the only enzyme in this system that is not a serine protease. The conversion of plasma factor XIII (A2B2) to the active transamidase factor XIIIa (A2) results from hydrolysis of the Arg36-Gly37 at the NH2-terminus of the A subunit by thrombin (13). Full expression of activity is achieved only after the Ca2+ (Kd-3M) and fibrin(ogen) (Kd-8M) dependent dissociation of the B subunit dimer from the A2 dimer (14-16). Specific Activity: ~40U/mg. 1unit is equal to the Factor XIII activity in 1ml normal plasma. Isoelectric Point: ~5 Structure: 2 pairs of identical subunits, A2B2. A2: Mr 75,000 B2: Mr 88,000 Carbohydrate Content: A chain: 1%, B chain: 5% Extinction Coefficient (1%, 1cm, 280nm): 13.8 Storage and Stability: May be stored at 4C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20C. Aliquots are stable for 6 months after receipt at -20C. 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.
Molekulargewicht:
320
Reinheit:
95%. Purified by barium citrate, ammonium sulfate and glycine precipitations, ion exchange chromatography and gel filtration. Verified by SDS-PAGE. Activity determined by clotting assay.
Formulierung:
Supplied in 0.5mM EDTA, 50% glycerol/H2O.
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