A kinetic analysis of the hydrolysis of synthetic arginine substrates by arginine esterases from the venom of the gabooon adder, Bitis gabonica

The kinetics of arginine esterases E-I, E-II and E-III from the venom of Bitis gabonica were investigated. With N alpha-benzoyl-L-arginine ethyl ester as substrate linear competitive inhibition versus L-arginine was observed while ethanol gave rise to S-parabolic I-linear noncompetitive inhibition. Hydrolysis of N alpha-benzoyl-L-arginine-p-nitroanilide was noncompetitively inhibited by p-nitroaniline. Both slopes and intercepts of double reciprocal plots were a linear function of inhibitor concentration. Ethanol gave complex inhibition kinetics which could be interpreted in terms of mixed dead-end and alternate product inhibition (S-parabolic I-hyperbolic noncompetitive inhibition). These results imply an ordered uni-bi as the minimal kinetic mechanism wherein ethanol (or amine when amide is used as substrate) is released first from the enzyme surface, followed by the liberation of arginine. The enzymes are inactivated by phenylmethane sulfonyl fluoride which suggests the presence of an essential serine in the active sites of the enzymes. The enzymes may therefore be classified in the group of serine proteases.

Molecular properties of the Factor V-activating enzyme from Russell's viper venom

The protease from Russell's viper venom that activates Factor V was purified by gel filtration on Sephadex G-150 and ion exchange column chromatography on sulfopropyl (SP)-Sephadex C-50. The purified enzyme is a glycoprotein containing 6% carbohydrate. It migrated as a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 29,000. A minimum molecular weight of 27,200 was determined by sedimentation equilibrium in the presence of 6 M guanidine hydrochloride. The enzyme is composed of a single polypeptide chain possessing an NH2-terminal sequence of Val-Val-Gly-Gly-Asp-Glu-Cys-Asn-Ile-Asn-Glu-His-Pro-Ile. The specific activity of the Factor V activator toward tosyl-L-arginine methyl ester and D-phenylalanyl-L-pipecolyl-L-arginyl-p-nitroanilide was 380 and 11 nmol/min/mg, respectively. The esterase and coagulant activities of the enzyme were readily inhibited by diisopropyl fluorophosphate. The enzyme was not inhibited by bovine antithrombin III in the presence or absence of heparin. The amino acid and carbohydrate compositions of the enzyme are also reported.

Bites by the carpet viper in the Niger Valley

60 people who had been bitten by the carpet viper, Echis carinatus, were seen in four months at Zungeru Health Centre, in North West Nigeria, where snake-bite patients have recently occupied 10% of beds. Health statistics greatly underestimate the frequency, morbidity, and mortality of snake bite in the rural tropics and further studies will probably confirm other areas endemic for E. carinatus within its vast distribution zone. Regular supplies of effective antivenom are crucial to gain a community's confidence in conventional, as opposed to traditional, treatment. Paramedical staff in a rural clinic can be trained in the definitive management and treatment, including successful antivenom therapy, of most snake-bite patients.

Comparative thermometric coagulation studies of plasmas from normal outbred Swiss Webster mice and persons

The functional capabilities of a thermometric clot-timer have been demonstrated in a comparative study of human and mouse plasma coagulation. The influence of some variables on coagulation times of mouse and human plasmas were examined in activated partial thromboplastin time, one-stage prothrombin time, and Russell's viper venom time assays. Mouse plasma coagulation times were generally shorter and more reproducible than those of human plasma. Optimal assay conditions are also described.

Adder bites in children

16 children with adder bites were admitted to hospital in Southampton in the years 1969--77. Two children were severely poisoned; these 2, and a 3rd, fulfilled suggested criteria for antivenom administration but they recovered without it. Three children had no treatment, and 9 children no analgesia. Prolonged morbidity was not seen in these children. Careful observation in hospital was the most important factor in management, with early clinical improvement obviating the need for antivenom.

Activation of decarboxyfactor X by a protein from Russell's viper venom. Purification and partial characterization of activated decarboxyfactor X

1. Incubation of decarboxyfactor X with the factor X-activating enzyme from Russell's Viper venom revealed the generation of amidase activity towards Bz-Ile-Glu-Gly-Arg-pNA, but not of activity in blood coagulation. 2. The rate of activation of both factor X and decarboxyfactor X depends on the ability of the zymogens to bind Ca2+. The relationship between Ca2+ concentration and velocity of the activation reaction is sigmoid in the case of factor X, but hyperbolic with decarboxyfactor X. 3. Activated decarboxyfactor X was purified by powder column electrophoresis. 4. Identical changes of primary structure accompanied the activation of factor X and decarboxyfactor X. Identical molecular weight and common antigenic determinants were found in factor Xa and decarboxyfactor Xa. The amino acid composition was identical except for 12 glutamic acid residues in decarboxyfactor Xa and gamma-carboxyglutamic acid residues in factor Xa. 5. Unlike factor X, activated factor X has a very low electrophoretic mobility in the presence of Ca2+ at pH 8.6. This is probably due to self association of factor Xa under the influence of Ca2+. The electrophoretic mobility of activated decarboxyfactor X is only slightly decreased compared to decarboxyfactor X in the presence of Ca2+.

[A technique of accelerated immunization of animals producing antivenom serum]

A technique of "fast" immunization, for antivenom serum production, is reported. Comparatively to the common technique, this fast method is characterized by more numerous immunizing injections (15 instead of 8) during the two first cycles of immunisation, higher venom doses and the lack of the rest period taking place between the two first cycles of immunization in the common technique. By this fast technique one may obtain a highly efficient anti-venmous serum within 2 1/2 to 3 months whereas the common technique needs 3 1/2 to 4 months to obtain the same results.