Navegando por Palavras-chave "prothrombin activator"
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- ItemSomente MetadadadosEffects of Lopap on human endothelial cells and platelets(Karger, 2001-05-01) Chudzinski-Tavassi, Ana Marisa [UNIFESP]; Schattner, M.; Fritzen, Marcio [UNIFESP]; Pozner, R. G.; Reis, C. V.; Lourenco, Dayse Maria [UNIFESP]; Lazzari, M. A.; FAPESP; Natl Acad Med; Consejo Nacl Invest Cient & Tecn; Universidade Federal de São Paulo (UNIFESP)Severe consumption coagulopathy has been detected in rats after Lopap (a prothrombin activator from Lonomia obliqua caterpillar bristles) infusion and in humans after accidental contact with L. obliqua bristles. However, platelet count and antithrombin (AT) levels were only modestly affected, suggesting that a different form of blood coagulation activation may be involved in this hemorrhagic syndrome. Here we describe that Lopap had no effect on aggregation of washed human platelets induced by several agonists, suggesting that it might not impair platelet function in vivo. AT was able to inhibit the amidolytic activity of thrombin generated by incubation of Lopap with prothrombin in a purified system, which maybe different from that generated by the prothrombinase complex in vivo. The surface expression of both ICAM-1 and E-selectin but not of VCAM-1 was upregulated by Lopap in cultured HUVEC, suggesting that it may behave differently from other mediators, such as thrombin and tumor necrosis factor-alpha. Copyright (C) 2002 S. Karger AG, Basel.
- ItemSomente MetadadadosIn vivo characterization of Lopap, a prothrombin activator serine protease from the Lonomia obliqua caterpillar venom(Elsevier B.V., 2001-06-01) Reis, C. V.; Farsky, SHP; Fernandes, B. L.; Santoro, M. L.; Oliva, MLV; Mariano, M.; Chudzinski-Tavassi, A. M.; FAPESP; Universidade de São Paulo (USP); Butantan Inst; Universidade Federal de São Paulo (UNIFESP)Increasing occurrence of hemorrhagic syndrome in man, caused by contact with Lonomia obliqua caterpillars, has been reported in Southern Brazil in the past 10 years. the L. obliqua venom causes a severe consumptive coagulopathy, which can lead to hemorrhagic syndrome. L. obliqua prothrombin activator protease (Lopap) is a 69-kDa prothrombin activator serine protease isolated from L. obliqua caterpillar bristle extract, which is able to evoke thrombus formation, unclottable blood, and fibrinogen depletion when injected into the blood stream of rats. the purified protein generated thrombin from prothrombin, able to clot purified human fibrinogen and plasma. A decrease in platelet count and inhibition of collagen-induced platelet aggregation were observed, as well as leukocyte infiltration in the lungs. Ln addition, we observed congestion and hemorrhage in renal glomeruli and necrosis in renal distal tubules. These data support the hypothesis that Lopap contributes to the clinical syndrome caused by human contact with L. obliqua, most probably through prothrombin activation, resulting in a consumption coagulopathy. (C) 2001 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosInsularinase A, a prothrombin activator from Bothrops insularis venom, is a metalloprotease derived from a gene encoding protease and disintegrin domains(Walter de Gruyter Gmbh, 2005-06-01) Modesto, JCD; Junqueira-de-Azevedo, ILM; Neves-Ferreira, AGC; Fritzen, M.; Oliva, MLV; Ho, P. L.; Perales, J.; Chudzinski-Tavassi, A. M.; Inst Butantan; Inst Burantan; Fiocruz MS; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP)The first low-molecular-mass metalloprotease presenting prothrombin activating activity was purified from Bothrops insularis venom and named insularinase A. It is a single-chain protease with a molecular mass of 22 639 Da. cDNA sequence analysis revealed that the disintegrin domain of the precursor protein is post-translationally processed, producing the mature insularinase A. Analysis of its deduced amino acid sequence showed a high similarity with several fibrin(ogen)olytic metalloproteases and only a moderate similarity with prothrombin activators. However, SIDS-PAGE of prothrombin after activation by insularinase A showed fragment patterns similar to those generated by group A prothrombin activators, which convert prothrombin into meizothrombin independently of the prothrombinase complex. in addition, insularinase A activates factor X and hydrolyses fibrinogen and fibrin. Chelating agents fully inhibit all insularinase A activities. Insularinase A induced neither detachment nor apoptosis of human endothelial cells and was also not able to trigger an endothelial proinflammatory cell response. Nitric oxide and prostacyclin levels released by endothelial cells were significantly increased after treatment with insularinase A. Our results show that, although its primary structure is related to class P-I fibrin(ogen)olytic metalloproteases, insularinase A is functionally similar to group A prothrombin activators.
- ItemSomente MetadadadosA prothrombin activator serine protease from the Lonomia obliqua caterpillar venom (Lopap) biochemical characterization(Elsevier B.V., 2001-06-01) Reis, C. V.; Portaro, FCV; Andrade, S. A.; Fritzen, M.; Fernandes, B. L.; Sampaio, CAM; Camargo, ACM; Chudzinski-Tavassi, A. M.; FAPESP; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP)Lonomia obliqua venom causes a severe consumptive coagulopathy, which can lead to a hemorrhagic syndrome. the crude bristles extract displays a procoagulant activity due to a Factor X and to a prothrombin activating activity. Here, we describe a 69 kDa prothrombin activator serine protease purified from L. obliqua caterpillar bristle extract using gel filtration (Sephadex G 75) and HPLC (C-4 column). the purified protein was able to activate prothrombin in a dose-dependent manner, and calcium ions increased this activity. the prothrombin-derived fluorogenic peptide (Abz-YQTFFNPRTGSQ-EDDnp) had its main cleavage site at the Arg-Thr bond. the kinetic parameters obtained for this substrate were K-mapp. of 4.5 muM, k(cat) of 5.32 s(-1), and a k(cat)/K-mapp of 1.2 x 10(6) M-1 s(-1). the prothrombin fragments generated by the purified enzyme corresponded to the molecular masses of prethrombin 2, fragment 1, fragment 2, and thrombin as seen in SDS-PAGE. the thrombin generated was able to clot purified fibrinogen. the partial amino acid sequence of the purified protein, named Lopap (L. obliqua prothrombin activator protease), showed no similarity to any known prothrombin activator. (C) 2001 Elsevier B.V. All rights reserved.