title: Isolation and characterization of a protein C activator from tropical moccasin venom.
abstract: A protease from the venom of the tropical moccasin (Agkistrodon bilineatus) that activates protein C was purified to homogeneity by ion-exchange and gel permeation chromatography. The purified protease is a glycoprotein, and exhibited a molecular weight of 35,000 and 38,000 in SDS-PAGE under non-reducing and reducing conditions, respectively. The purified protease readily activated human protein C and steady-state kinetic parameters indicated an apparent Km for human protein C of 1.7 microM and an apparent kcat of 0.02 sec-1. Calcium inhibited the activation of human protein C by the venom protease (Ki = 93 microM). Amino-terminal sequence analysis revealed that the tropical moccasin protein C activator was highly homologous to the protein C activator isolated from Southern copperhead venom.
authors.affiliation: Blood Systems Research Foundation Laboratory, Department of Pathology, University of New Mexico School of Medicine, Albuquerque.
authors.forename: T
authors.initials: T
authors.lastname: Nakagaki
authors.forename: A L
authors.initials: AL
authors.lastname: Kazim
authors.forename: W
authors.initials: W
authors.lastname: Kisiel
mesh_terms: D000577:Amides / Q000378:metabolism; D000595:Amino Acid Sequence; D003435:Crotalid Venoms / Q000032:analysis*; D006801:Humans; D008969:Molecular Sequence Data; D011486:Protein C / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D012697:Serine Endopeptidases / Q000302:isolation & purification* / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology
chemical_list: C031442:Agkistrodon venoms; D000577:Amides; D003435:Crotalid Venoms; D011486:Protein C; D015842:Serine Proteinase Inhibitors; C065333:AB-C protease; D012697:Serine Endopeptidases