Biochemical and biological evaluation of gyroxin isolated from Crotalus durissus terrificus venom

Gyroxin, a thrombin-like enzyme isolated from Crotalus durissus terrificus venom and capable of converting fibrinogen into fibrin, presents coagulant and neurotoxic activities. The aim of the present study was to evaluate such coagulant and toxic properties. Gyroxin was isolated using only two chromatographic steps - namely gel filtration (Sephadex G-75) and affinity (Benzamidine Sepharose 6B) - resulting in a sample of high purity, as evaluated by RP-HPLC C2/C18 and electrophoretic analysis that showed a molecular mass of 30 kDa. Gyroxin hydrolyzed specific chromogenic substrates, which caused it to be classified as a serine proteinase and thrombin-like enzyme. It was stable from pH 5.5 to 8.5 and inhibited by Mn²+, Cu²+, PMSF and benzamidine. Human plasma coagulation was more efficient at pH 6.0. An in vivo toxicity test showed that only behavioral alterations occurred, with no barrel rotation. Gyroxin was not able to block neuromuscular contraction in vitro, which suggests that its action, at the studied concentrations, has no effect on the peripheral nervous system.

Two related thrombin-like enzymes present in Bothrops atrox venom

This article describes the presence of two new forms of a thrombin-like enzyme, both with apparent molecular masses of 38 kDa, in Bothrops atrox venom. Both share the ability to cleave fibrinogen into fibrin and to digest casein. Both present identical Km on the substrate BApNA. Their N-terminal amino acid sequences are identical for 26 residues, sharing 80 percent homology with batroxobin and flavoxobin. Two groups of monoclonal antibodies (mAbs) raised against the purified enzyme forms recognized different epitopes of the putative corresponding enzymes present in B. atrox crude venom. On Western blotting analysis of B. atrox crude venom, mAbs 5DB2C8, 5AA10 and 5CF11, but not mAbs 6CC5 and 6AD2-G5, revealed two or more protein bands ranging from 25 to 38 kDa. By immunoprecipitation assays, the 6AD2-G5 mAb was able to precipitate protein bands of 36-38 kDa from B. atrox, B. leucurus, B. pradoi, B. moojeni, B. jararaca and B. neuwiedii crude venoms. Fibrinogen-clotting activity was inhibited when the same venom specimens were pre-incubated with mAb 6AD2-G5, except for B. jararaca and B. neuwiedii

Produccion de Trombina y Tromboplastina tisular para el diagnostico de alteraciones hemorragicas y tromboticas / Production of Thrombim and Tromboplastim for diagnosis of hemorrhagic and thombotic disorders

Se produjo trombina a partir de plasma humano y tromboplastina de cerebro de conejo, se realizo el control de calidad de la trombina mediante (TT) y tiempo de Protrombina (PT) respectivamente, en muestras normales y patologicas. Se obtuvo una trombina de muy alta actividad y un rendimiento del reactivo suficiente para la determinacion de 2500 pruebas de TT. Asimismo se obtuvo tromboplastina de buena calidad con un rendimiento del reactivo suficiente para 240 pruebas a partir de 6,7 g de cerebro.