title: Catroxobin, a weakly thrombin-like enzyme from the venom of Crotalus atrox. NH2-terminal and active site amino acid sequences.
abstract: Two thrombin-like isoenzymes, termed catroxobins, were purified by gel filtration and ion exchange chromatography to electrophoretic homogeneity from the venom of the Western diamondback rattlesnake, Crotalus atrox. By SDS-polyacrylamide gel electrophoresis their molecular weights were estimated to be 25,000 and 26,200. A 43-residue NH2-terminal sequence, containing the active histidine residue, was the same for the two isoenzymes. In addition, a 33-residue internal peptide from catroxobin I contained a normal active serine sequence. These sequences were highly homologous to other thrombin-like venom enzymes, and to pancreatic kallikrein and trypsin, but less so to the B chain of thrombin. Catroxobin, possessing 89 TAME esterase units/mg of protein, clotted human fibrinogen very slowly, releasing fibrinopeptide A and a small amount of fibrinopeptide B. No other evidence of cleavage of the fibrinogen molecule was revealed by polyacrylamide gel electrophoresis or HPLC.
authors.affiliation: Department of Pathology, University of California, Irvine 92717.
authors.forename: H
authors.initials: H
authors.lastname: Pirkle
authors.forename: I
authors.initials: I
authors.lastname: Theodor
authors.forename: R
authors.initials: R
authors.lastname: Lopez
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003435:Crotalid Venoms / Q000302:isolation & purification*; D007527:Isoenzymes / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012689:Sequence Homology, Nucleic Acid; D012697:Serine Endopeptidases / Q000302:isolation & purification*
chemical_list: D003435:Crotalid Venoms; D007527:Isoenzymes; D012697:Serine Endopeptidases; C062780:catroxobin