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Purification, characterization and cDNA cloning of a phospholipase A2 inhibitor from the serum of the non-venomous snake Elaphe quadrivirgata.

ABSTRACT: The serum of a non-venomous striated snake, Elaphe quadrivirgata, was found to contain phospholipase A2 (PLA2) inhibitory proteins (PLIs). One of these inhibitors was purified by Sephadex G-200 gel filtration, Q-Sepharose FF ion-exchange chromatography and Butyl Sepharose 4FF hydrophobic chromatography. The purified PLI inhibited the enzymic activities of all PLA2 groups, including Elapidae venom (group-I), Viperidae venom (group-II) and honeybee PLA2s (group-III). The inhibitor was a 130 kDa glycoprotein consisting of two distinct subunits, A and B, of 30 and 29 kDa respectively; each of which was glycosylated with N-linked oligosaccharide chains. The cDNAs encoding the respective inhibitor subunits were isolated from a liver cDNA library by the use of probes, prepared by PCR, based on the partially determined amino-acid sequences of the corresponding subunits. The respective nucleotide sequences encoded 19-amino-acid-residue signal sequences, followed by 183- and 181-residue protein sequences for the A and B subunits respectively. The amino-acid sequences revealed that the E. quadrivirgata inhibitor corresponded to PLIgamma, one of three kinds of inhibitors purified from venomous snakes. The existence of PLIgamma in the serum of this non-venomous snake suggested that, besides having a protective role against the venom PLA2s of other venomous snakes, PLIgamma has other important physiological functions in regulating local PLA2 activities; and thus it raises the possibility that PLIgamma occurs in other animals, including mammals.

SUBMITTER: Okumura K

PROVIDER: S-EPMC1220343 | biostudies-other | 1999 Jul

REPOSITORIES: biostudies-other

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Purification and characterization of the first γ-phospholipase inhibitor (γPLI) from Bothrops jararaca snake serum.

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Project description:Background:Snake venom phospholipases A2 (PLA2s) have been reported to induce myotoxic, neurotoxic, hemolytic, edematogenic, cytotoxic and proinflammatory effects. This work aimed at the isolation and functional characterization of a PLA2 isolated from Bothrops jararaca venom, named BJ-PLA2-I. Methods and Results:For its purification, three consecutive chromatographic steps were used (Sephacryl S-200, Source 15Q and Mono Q 5/50 GL). BJ-PLA2-I showed acidic characteristics, with pI~?4.4 and molecular mass of 14.2 kDa. Sequencing resulted in 60 amino acid residues that showed high similarity to other Bothrops PLA2s, including 100% identity with BJ-PLA2, an Asp49 PLA2 previously isolated from B. jararaca venom. Being an Asp49 PLA2, BJ-PLA2-I showed high catalytic activity, and also inhibitory effects on the ADP-induced platelet aggregation. Its inflammatory characterization showed that BJ-PLA2-I was able to promote leukocyte migration in mice at different concentrations (5, 10 and 20 ?g/mL) and also at different response periods (2, 4 and 24 h), mainly by stimulating neutrophil infiltration. Furthermore, increased levels of total proteins, IL-6, IL-1? and PGE2 were observed in the inflammatory exudate induced by BJ-PLA2-I, while nitric oxide, TNF-?, IL-10 and LTB4 levels were not significantly altered. This toxin was also evaluated for its cytotoxic potential on normal (PBMC) and tumor cell lines (HL-60 and HepG2). Overall, BJ-PLA2-I (2.5-160 ?g/mL) promoted low cytotoxicity, with cell viabilities mostly varying between 70 and 80% and significant values obtained for HL-60 and PBMC only at the highest concentrations of the toxin evaluated. Conclusions:BJ-PLA2-I was characterized as an acidic Asp49 PLA2 that induces acute local inflammation and low cytotoxicity. These results should contribute to elucidate the action mechanisms of snake venom PLA2s.

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