title: Cerastocytin, a new thrombin-like platelet activator from the venom of the Tunisian viper Cerastes cerastes.
abstract: Cerastocytin, a thrombin-like enzyme from the venom of the desert viper, Cerastes cerastes, has been purified to homogeneity by fast performance liquid chromatography (FPLC) on Mono-Q and Mono-S columns. It is a basic protein (isoelectric point higher than 9) made of a single polypeptide chain of 38 kDa. Its N-terminal polypeptide sequence shows strong similarities with other thrombin-like enzymes from snake venoms. Nanomolar concentrations of cerastocytin induce aggregation of blood platelets. This activity is inhibited by chlorpromazine, theophylline and mepacrine, as in the case of platelet aggregation stimulated by low doses of thrombin. Cerastocytin also possesses an amidolytic activity measured with the thrombin chromogenic substrate S-2238. The platelet aggregating activity and the amidolytic activity of cerastocytin were inhibited by PMSF, TPCK, TLCK and soybean trypsin inhibitors, suggesting that cerastocytin is a serine proteinase. On the other hand, both amidolytic activity and platelet aggregating activity of cerastocytin were unaffected by hirudin or by antithrombin III in the presence of heparin. High concentrations of cerastocytin (1-10 microM) also cleaved prothrombin and Factor X.
authors.affiliation: Unité des Venins, Institut Pasteur, Paris, France.
authors.forename: N
authors.initials: N
authors.lastname: Marrakchi
authors.forename: R B
authors.initials: RB
authors.lastname: Zingali
authors.forename: H
authors.initials: H
authors.lastname: Karoui
authors.forename: C
authors.initials: C
authors.lastname: Bon
authors.forename: M
authors.initials: M
authors.lastname: el Ayeb
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001777:Blood Coagulation / Q000187:drug effects; D008969:Molecular Sequence Data; D008970:Molecular Weight; D015539:Platelet Activation / Q000187:drug effects*; D011516:Prothrombin / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013917:Thrombin / Q000737:chemistry / Q000302:isolation & purification*; D014757:Viper Venoms / Q000737:chemistry / Q000201:enzymology*
chemical_list: D015842:Serine Proteinase Inhibitors; D014757:Viper Venoms; D011516:Prothrombin; D012697:Serine Endopeptidases; C093951:cerastocytin; D013917:Thrombin