Human Factor XII (XII) (Hageman Factor) is a single chain (78kD) glycoprotein zymogen that circulates in plasma at a concentration of 40 mg/ml. Reciprical activation of XII to the active serine protease factor XIIa (XIIa) by kallikrein is central to initiation of the intrinsic coagulation pathway. Surface bound a-XIIa in turn activates factor XI to XIa. A single cleavage by kallikrein at R353-Val354 of XII yields a-XIIa, a 2 chain protease (80kD) held together by disulfide bonds. The COOH-terminal light chain (28kD) contains the catalytic triad (His-40, Asp-89, Ser-191), while the NH2-terminal heavy chain (52kD) conatins the anionic surface binding portion of the molecule. A secondary cleavage of a-XIIa by kallikrein outside the disulfide bond yields b-XIIa (XIIf, BHFa, HFf, hageman factor fragments) (28kD), which no longer binds anionic surfaces. b-XIIa can activate prekallikrein, but has little procoagulant activity. Inhibitors of XIIa include C1-INH, a2-antiplasmin, a2-macroglobulin and antithrombin III. At physiological concentrations, the relative effectiveness of these inhibitors is 91: 4.5:3:1.5, respectively. The ratio of C1-INH to XII has been implicated in the ''cold activation of factor VII and the conversion of prorenin to renin on storage of plasma. Applications: Suitable for use in ELISA, Inhibition and Coagulation assays. Other applications not tested. Recommended Dilutions: Optimal dilutions to be determined by the researcher. 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 12 months after receipt. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.
Clonality:
Monoclonal
Clone Designation:
[1.B.694]
Isotype:
IgG1
Purity:
Purified by Protein G affinity chromatography from ascites.
Form:
Supplied as a liquid in PBS, pH 7.4. No preservative added.
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