Venom phospholipase A: A review

Molecular Cloning and Functional Analysis of Secretory Phospholipase A2 from Apostichopus japonicus

Secretory phospholipase A2 (sPLA2) plays important roles in phospholipid metabolism, skin barrier maintenance, immune response and other processes in organisms. sPLA2 of sea cucumber A. japonicus (AjPLA2) has not yet been reported. This study successfully amplified the AjPLA2 sequence. The total cDNA of AjPLA2 is 931 bp, including a 480 bp ORF that encodes 159 amino acids. The AjPLA2 protein includes a 16-aa signal peptide, a 5-aa precursor peptide and a 138-aa mature peptide. Homologous alignment showed that AjPLA2 and the sPLA2s from starfish have the typical domains of the Group IB sPLA2. And additional amino acid sequences were found around the β-Wing, which is different from the Group IB sPLA2. These results showed that AjPLA2 and sPLA2s from starfish all belong to a new group in the Group I sPLA2 family. AjPLA2 is widely distributed in sea cucumber tissues. The functional analysis also showed that AjPLA2 was upregulated in the intestine by feeding. When the body wall was damaged, it was significantly upregulated around the wound. And the expression levels of AjPLA2 were significantly increased in V. splendens-infected sea cucumbers. The results indicated that AjPLA2 plays roles in the sea cucumber immunologic process. Combined with the upregulation of unsaturated fatty acids (PUFAs) content in A. japonicus, it demonstrated that AjPLA2 could participate in the immune of A. japonicus by hydrolyzing phospholipid and releasing PUFAs. This study had a solid foundation for the further research of AjPLA2 gene function in vivo, development and application of AjPLA2 protein.

Hepatotoxicity induced by the Oriental hornet (Vespa orientalis) venom sac extract

Experiments were performed to investigate the nature of the in vitro and human liver damage exposed to hornets' acute or repeated stings. The hornet investigated is the one ubiquitous in Israel - Vespa orientalis. Experiments were performed in living cats and rats, after single or multiple exposures to venom-sac extracts (VSE) and in various doses. The injury was demonstrated by the increased levels of enzymes, bile acids and cholesterol in serum. Also measured was Beta-N-acetyl hexosaminidase (BNAH) which probably is the only biochemical indicator available of Kupffer-cell function. This, too, was found increased. Other experiments consisted of perfusion of the isolated, intact, rat liver in situ with measurements of enzyme leakage into perfusate and of bile flow. Another set of experiments involved the effects of VSE on in vitro monolayer tissue culture of rat embryos' livers. We examined damage to organelles and compared the damage produced by intact VSE with that produced by the venom sac extract after treatment by heat or dialysis. Light morphology, special stains, electron microscopy and morphometry were all performed. In the first set of experiments no shock was observed in cats and rats exposed to VSE. The increases in enzymes' activity in serum and liver perfusion fluid were significant. Histochemistry indicated decrease of hepatic glycogen and of cellular succinic dehydrogenase as well as hepatic fat infiltration and an increase of alkaline phosphatase activity in liver cells close to the bile capillaries.(ABSTRACT TRUNCATED AT 250 WORDS)

Phospholipase A2 in venom extracts from honey bees (Apis mellifera L.) of different ages

We measured phospholipase A2 activity in the venom of worker honey bees (Apis mellifera L.) of known ages using chemical (titrimetric) and radioallergosorbent methods. The two techniques give similar results. Low levels of phospholipase A2 are present in the venom system at the time of eclosion. Phospholipase A2 activity in the venom increases steadily through the 10 days after eclosion. Maximal phospholipase A2 levels (about 40 micrograms phospholipase A2/venom sac) are maintained through the rest of the life of a worker bee in summer.

Phospholipases B from Japanese yellow hornet (Vespa xanthoptera) venom

Two phospholipases B (Vx I and Vx II) were purified from the venom of the Japanese yellow hornet, Vespa xanthoptera, by sequential chromatography on Sephadex G-100, SP-Sephadex and Mono S columns. They are very similar to each other in molecular and enzymatic properties, though the specific activity of Vx I was one-fifth that of Vx II. They hydrolyze the acyl ester bonds at the 1-position of phosphatidylcholine and lysophosphatidylcholine, therefore, their enzymatic specificities were of the A1 and L1 types.

Toxicity to crustacea due to polypeptide-phospholipase interaction in the venom of a chactoid scorpion

The toxic factors to isopods (crustacea) were isolated from the venom of the chactoid scorpion Scorpio maurus palmatus (Scorpionidae) by the aid of column chromatography, and their purity was assessed by disc electrophoresis, analytical ultracentrifugation, isoelectrofocusing, and amino acid analysis. The toxicity to isopods is attributed to two groups of components: (a) Low-molecular-weight basic polypeptides possessing about 3 and 8% of the crude venom lethality and paralytic potency to isopods, respectively. These components are characterized by very similar and unique amino acid compositions of 31 to 34 amino acids with molecular mass of about 3.5 kDa and a deficiency in methionine, leucine, phenylalanine, histidine, and tryptophan. (b) Toxic phospholipases are also toxic to insect but not to mammals. A lethal phospholipase which contained 37% of the total venom phospholipase activity and 11% of its toxicity to isopods was purified. This phospholipase consists of 125 amino acids (Mr 14,581) and is a hydrophobic, acidic protein composed of two isoenzymes (pI 4.7 and 4.9). This enzyme demonstrates an A2-type positional specificity (EC 3.1.1.4) with pH and temperature optima of 7.5-8.0 and 40-50 degrees C, respectively, and high calcium requirements. The lethal potency of the basic polypeptides is evidently increased by the addition of low, sublethal doses of the pure phospholipase. Such synergism was not observed with regards to their paralytic activity. The pharmacological significance of these data is discussed.

Amino-acid sequence of the beta 1 isosubunit of taipoxin, an extremely potent presynaptic neurotoxin from the Australian snake taipan (Oxyuranus s. scutellatus)

The amino acid sequence of the beta 1 isosubunit of taipoxin, an extremely potent presynaptic neurotoxin from the Australian snake taipan, has been determined. The beta 1 isosubunit, which is neither toxic nor enzymatically active on its own, consists of a single polypeptide chain of 118 amino acids. The main fragmentation of the reduced and S-carboxymethylated derivative was accomplished by cleavage with Staphylococcus aureus V8 protease. Tryptic peptides were used to align and complete the sequence, which was determined by automated Edman degradation. The taipoxin beta 1 isosubunit is closely homologous to the taipoxin alpha and gamma subunits and to enzymatically active pancreatic and elapid snake venom phospholipases A2.

A phospholipase A2 with anticoagulant activity. I. Isolation from Vipera berus venom and properties

An anticoagulant protein has been isolated by DEAE cellulose chromatography and gel filtration from the venom of the Vipera berus orientale (Eastern Europe). Purification has been completed by elution on carboxymethyl cellulose with continuous gradient at constant pH. The inhibitor of coagulation was separated from the other venom enzymes, e.g. procoagulant, fibrinogenolytic, aminoesterase and amino acid oxidase activities. It was also separated from other phospholipase components which were not related to the anticoagulant property. The inhibitor appeared as a simgle polypeptidic chain protein, formed by 119 amino acid residues, with a molecular weight of 13400 and an isoelectric point of 9.2. At low saline molarity, a monomer-trimer transition of this protein was observed. Both forms had the same amino acid composition. There were six disulfide bridges without free SH groups per phospholipase molecule. Deprived of any proteolytic activity, the clotting inhibitor displayed a high phospholipase activity in the presence of calcium. Activity did no appear with EDTA buffer deprived of cation. Finely dispersed micellar suspensions were found suitable for obtaining the highest phospholipase activity. High sodium cholate concentration or methanol/chloroform/ether solvent were effective without loss of enzymatic activity. As characteristis of phospholipase A2 (EC 3.1.1.4), the degradation products identified on thin-layer chromatography induced hemolysis of human erythrocytes. The apparent Km value 1.25 - 10(-3) M was determined on phosphatidylcholine isolated from ovolecithin. This purified berus inhibitor would be of value for investigating the involvement of phospholipids in the clotting mechanism.

Comparison of honeybee venoms and their components from various sources

The use of honeybee venoms and their components may assist in the elucidation of the pathophysiology of reactions to honeybee stings. This initial study compared venoms from various sources by chemical and biological assays, and significant variations were observed. Ten different bee venoms were compared by nitrogen analysis, mouse toxicity, hyaluronidase content, and antigenicity. Based on mouse toxicity, hyaluronidase content, and gel diffusion analysis, two groups of bee venoms could be differentiated. Venoms in one group, Group A, were more toxic, contained hyaluronidase, and showed an additional precipitin band. All venoms contained mellitin as a major fraction, which formed nonimmune precipitin bands during gel diffusion analysis. Gel filtration chromatography and dialysis separated the venoms into components that were then identified by enzyme assays, rat mast cell degranulation, hemolytic activity, and gel diffusion analysis. The venoms within Group A showed similar components, some of which, most noticeably hyaluronidase, were not present in Group B. Dialysis showed that a large portion of the venom could pass through a cellophane membrane including a portion of the phospholipase A. Heterogeneous molecular weights were found for phospholipase A by both gel filtration and dialysis, and may reflect variation in carbohydrate content. It appears that bee venom variability for whatever reason, a heterogeneous MW antigen, and a non-immune precipitable component require careful consideration in any study involving this venomm. These studies have yielded relatively pure, identified bee venom components which can be employed in further studies investigating reactions to honeybee stings.