Activation of human prothrombin by a procoagulant fraction from the venom of Echis carinatus. Identification of a high molecular weight intermediate with thrombin activity.

摘要: In the presence of a procoagulant fraction (Echis carinatus procoagulant) isolated from venom saw-scaled viper Echis sochureki, purified human prothrombin (P1) is completely converted to thrombin. The first step removal an NH2-terminal peptide (F1) representing approximately one-third molecule. remaining (P2) then cleaved by action E.c. yield two-chain, disulfide-bridged protein (P'2) which has same molecular weight as P2. P'2 enzymic (thrombin) activity, evidence incorporation radiolabeled diisopropylphosphate into its heavy chain (TB), hydrolysis p-toluenesulfonylarginine methyl ester, and clotting fibrinogen. Relative thrombin, esterolytic activity greatly exceeds clot-promoting activity. Examination polypeptide chains obtained reducing shown that larger (TB) indistinguishable Its other (F2TA) consists light (TA) thrombin bound linkage protion molecule had been adjacent F1. Removal this portion (F2) catalyzed (and, evidently, P'2), but not procoagulant. When F2 removed P'2, two-chian any criteria applied--molecular weight, subunit composition, or Polyacrylamide gel electrophoresis was carried out in sodium dodecyl sulfate before after disulfide reduction samples generated absence diisopropylphosphorofluoridate, inhibits Such experiments showed (and probably well procoagulant, catalyzes release Furthermore, brings about cleavage F1 disulfidebridged (F'1). These observations, particularly those made course characterizine have led conclusion bond connecting TA TB portions (or derivatives) produces serine active center and, hence, possessing This thrombon itself.