title: Factor X activating enzyme from Russell's viper venom: isolation and characterization.
abstract: The protease from Russell's viper venom that activates factor X (Stuart factor), factor IX (Christmas factor), and protein C was purified by gel filtration on Sephadex G-150 and QAE-Sephadex A-50 column chromatography. The purified enzyme migrated as a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 79 000. A minimal molecular weight of 78 500 +/- 800 was determined by sedimentation equilibrium in the presence of 6 M guanidine hydrochloride. Upon reduction with 2-mercaptoethanol, a heavy chain (mol wt 59 000) and a light chain were observed. The light chain migrated as a single band (mol wt 19 000) in 7.5% polyacrylamide-sodium dodecyl sulfate gels but appeared as a doublet (mol wt 18 000 and 20 000) in 10% polyacrylamide-sodium dodecyl sulfate gels. The amino-terminal end of the heavy chain was heterogeneous and contained isoleucine, valine and serine. The amino-terminal sequence of the light chain was Val-Leu-Asp. The factor X activator contained 13% carbohydrate including 6.0% hexose, 1.7% N-acetyleneuraminic acid, and 5.3% galactosamine. Most of the carbohydrate was found to be present in the heavy chain, although some was also observed in both forms of the light chain. The factor X activator had no esterase activity toward benzoyl-Phe-Val-Arg-p-nitroanilide or benzoylarginine ethyl ester and was not inhibited by 0.05 M diisopropyl phosphorofluoridate. These data indicate that factor X activator from Russell's viper venom is a highly specific protease composed of one heavy chain and one light chain, and these chains are held together by a disulfide bond(s).
mesh_terms: D000116:Acetylgalactosamine / Q000032:analysis; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002097:C-Reactive Protein / Q000378:metabolism; D004789:Enzyme Activation; D005164:Factor IX / Q000378:metabolism; D005170:Factor X / Q000378:metabolism*; D006601:Hexoses / Q000032:analysis; D006801:Humans; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000302:isolation & purification / Q000378:metabolism; D012794:Sialic Acids / Q000032:analysis; D012910:Snake Venoms / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D006601:Hexoses; D012794:Sialic Acids; D012910:Snake Venoms; D005164:Factor IX; D005170:Factor X; D002097:C-Reactive Protein; D010447:Peptide Hydrolases; D000116:Acetylgalactosamine