Crotalus atrox venom contains a variety of proteases which render fibrinogen incoagulable and solubilize fibrin. One of these proteases was purified by using ion-exchange and gel permeation liquid chromatography. The protease, called atroxase, consists of a single nonglycosylated polypeptide chain with a molecular weight of 23,500 and an isoelectric point of pH 9.6. Amino acid analysis indicates atroxase to contain 206 residues with no sulfhydryl groups. Metal analysis found zinc and potassium at 1 mol/mol of protein, and calcium at 0.3 mol/mol of protein. Proteolytic activity is inhibited by ethylenediaminetetraacetate and alpha 2-macroglobulin. Maximal proteolytic activity occurs at pH 9.0 and 55 degrees C. Proteolytic specificity, using oxidized insulin B chain, is similar to that of several hemorrhagic toxins found within the same venom, yet atroxase shows no hemorrhagic activity and exhibits low lethality when tested on Swiss Webster mice. Atroxase, an A alpha, B beta fibrinogenase, cleaves the A alpha chain of fibrinogen first followed by the B beta chain and shows no effect on the gamma chain. The nonspecific action of the enzyme results in the extensive hydrolysis of fibrinogen which releases a variety of fibrinopeptides. Fibrin solubilization appears to occur primarily from the hydrolysis of alpha-polymer and unpolymerized alpha and beta chains. Although crude venom induces platelet aggregation, atroxase demonstrated no ability to induce or inhibit aggregation.

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Abstract:A quantitative method for the determination of potato lectin activity has been developed. In the method, lectin is incubated with an excess of red blood cells (RBC) in phosphate buffered saline at 25 "C. Maximum agglutination is reached within 60 min. Agglutinated RBC are then separated from nonagglutinated RBC by filtration. The agglutinated RBC remaining on the filter paper are then lysed and eluted using a solution of Triton X-100. The hemoglobin content of the lysed RBC is measured at 415 nm. The number of agglutinated RBC is calculated from the hemoglobin value. One unit of lectin activity will agglutinate one million RBC.