Activated protein C (APC) is an anticoagulant serine protease derived from the two chain, vitamin K-dependent zymogen, protein C (3-7). A complex between alpha-thrombin and thrombomodulin catalyzes a single cleavage at Arg-12 (Arg-14 in bovine) in the heavy chain of protein C, to generate activated Protein C. Several non-physiologically relevant proteases such as RVV-X activator, trypsin, and PROTAC are also capable of activating protein C. APC functions as an anticoagulant which catalyzes the proteolytic inactivation of the cofactors, factors Va and VIIIa, leading to inhibition of the prothrombinase and factor Xase complexes. The inactivation of factors Va and VIIIa is both Ca2+ and phospholipid dependent. The vitamin K dependent cofactor, protein S, moderately increases this rate of inactivation by forming a 1:1 complex with APC (Kd=6x10-9M) (8). Several factors attenuate the anticoagulant activity of APC. Factor Xa protects factor Va from proteolysis by APC by competing for a similar binding site on factor Va. Thrombin has also been proposed as a regulator of APC by proteolytic inactivation of protein S. In addition, APC is regulated by a circulating heparin-dependent protein C inhibitor (PAI-3), a circulating heparin-independent protein C inhibitor, a platelet-derived protein C inhibitor, and PAI-1. The complexes formed between APC and both types of PAI have been reported to account for increased fibrinolysis observed upon infusion of APC or the generation of APC in vivo. Localization: Plasma Mode of Action: Anticoagulant, inactivates factors Va and VIIIa Extinction Coefficient: E1%1cm, 280nm = 13.7 (9) Isoelectric Point: 4.2-4.5 (9) Structure: Two chains, Mr=35,000 and 21,000, disulfide linked, NH2-terminal gla domain two EGF domains Percent carbohydrate: 14% (5) Post-translational Modifications: Eleven gla residues, one beta-hydroxyaspartate 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 at least 6 months 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.
Molecular Weight:
52650
Purity:
Purified by Ion Exchange chromatography (~95% SDS-PAGE).
Form:
Supplied as a liquid 20mM Hepes, pH 7.4, 150mM sodium chloride.
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