title: Proteolytic specificity of hemorrhage toxin a isolated from western diamondback rattlesnake (Crotalus atrox) venom.
abstract: The proteolytic specificity of hemorrhagic toxin a from the venom of Crotalus atrox (western diamondback rattlesnake) has been investigated by using the oxidized B chain of bovine insulin and other peptides as substrates. The toxin appears highly specific for X--Leu bonds (cleaving the His10--Leu11, Ala14--Leu15, and Tyr16--Leu17 bonds), with no detectable activity against the Gly--Phe, Phe--Phe, Phe--Tyr, and Leu--Tyr bonds also present in the insulin B chain. The X--Leu bond of the peptides Tyr-Gly-Gly-Phe-Leu, Phe-Ala-Leu, and Ala-Leu was also cleaved. The toxin seems to be a strict endopeptidase, in that the cleavage of the two most susceptible bonds, Ala14--Leu15 and Tyr16--Leu17, are mutually exclusive; i.e., cleavage of either bond results in the other being too close to either the amino- or carboxyl-terminal of its respective fragment for the enzyme to be effective against it. The X--Met bond of Tyr-Gly-Gly-Phe-Met was cleaved, although a dipeptide Gly-Met was not hydrolyzed after 16 h of incubation. The substrates not hydrolyzed are furylacryloylglycyl-L-leucinamide, carbobenzoxy-L-glutamylglycine, carbobenzoxyglycyl-L-glutamic acid, benzoyl-L-arginine-p-nitroanilide, L-lysine-p-nitroanilide, (L-Ala)3-p-nitroanilide, Gly-Met, Gly-Phe-Phe, Gly-Gly-Ala, TAME, and ATEE. The absence of hydrolytic activity against the last two substrates indicates that hemorrhagic toxin a does not possess trypsin- or chymotrypsin-like activity.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002855:Chromatography, Thin Layer; D003435:Crotalid Venoms / Q000302:isolation & purification*; D006470:Hemorrhage / Q000139:chemically induced; D007328:Insulin; D007700:Kinetics; D010446:Peptide Fragments / Q000032:analysis; D010447:Peptide Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D003435:Crotalid Venoms; D007328:Insulin; D010446:Peptide Fragments; D010447:Peptide Hydrolases