Phospholipase venom

Hydrolytic enzymes phospholipases in snake venoms, endogenous... 

The venoms of poisonous snakes contain (among other things) a class of enzymes known as phospholipases, enzymes that cause the breakdown of phospholipids. For example, the venoms of the eastern diamondback rattlesnake (Crotalus adamanteus) and the Indian cobra Naja naja) both contain phospholipase Ag, which catalyzes the hydrolysis of fatty acids at the C-2 position of glyc-erophospholipids. 

A second group of myotoxic toxins, found almost exclusively in the venoms of cobras, are the cytotoxins (often called cobratoxins, cytolysins, cardiotoxins, or direct lytic factors). These, rather than phospholipases, are almost certainly the primary cause of muscle damage following bites by cobras. Their mechanism of action is not properly known, but it is certainly the case that their action is potentiated by the presence of phospholipases in the venom, even if the phospholipases concerned are not, themselves, myotoxic. The cytotoxins of cobra venom possess no hydrolytic activity of any kind. 

Harris, J.B. (1990). Phospholipases in snake venoms and their effects on nerve and muscle. In Snake Toxins (Harvey, A.L., ed.), pp. 91-129, Pergamon Press, Oxford. 

Bumble bee venom contains also a phospholipase A2 with partial identity to bee venom phospholipase Aj and a protease, but no melittin. Instead there are several small peptides called bombolitins [9]. There is limited cross-reactivity between honey bee and bumblebee venoms [2]. 

Major allergens in all vespid venoms are phospholipase A, a 33.5-kDa enzyme which digests cell membranes (Ves vl for V vulgaris) and antigen 5 (Ves v5), a 23-kDa... 

A number of allergens from both honey bee and vespid venoms have been cloned and expressed by either Escherichia coli or baculovirus-infected insect cells (table 1) phospholipase Aj [20], hyaluronidase [21], acid phosphatase [13] and Api m6 [14] from honey bee venom, as well as antigen 5 [22], phospholipase A and hyaluronidase [23] from vespid venom, and dipeptidylpeptidases from both bee and Vespula venoms [15, 16]. Their reactivity with human-specific IgE antibodies to the respective allergens has been documented [11-16, 22, 23] and their specificity is superior... 

Immunologic abnormahties (eg, transfusion reactions, the presence in plasma of warm and cold antibodies that lyse red blood cells, and unusual sensitivity to complement) also fall in this class, as do toxins released by various infectious agents, such as certain bacteria (eg, Clostridium). Some snakes release venoms that act to lyse the red cell membrane (eg, via the action of phospholipases or proteinases). 

Phospholipase A activity was subsequently demonstrated to be present in venom, and it too required Ca (25). DEAE-cellulose fractionation yielded four proteins, two of which were phospholipase A and hemolytic, and two of which had neither phospholipase A nor hemolytic activities. Either of the latter two proteins enhanced to various degrees the hemolytic activity of either of the two phospholipases. The findings suggest considerable analogy with synergistic mechanisms underlying the hemolytic action of the venoms of a number of snakes. 

While most investigations show that sea snake neurotoxins are postsynaptic type, Gawade and Gaitonde (23) stated that Enhydrina schistosa major toxin has dual actions or postsynaptic as well as presynaptic toxicity. E, schistosa venom phospholipase A is both neurotoxic and myotoxic. Neurotoxic action of the enzyme is weak so that there is sufficient time for myonecrotic action to take place (24), Sea snake, L. semifasciata toxin also inhibits transmission in autonomic ganglia, but has no effect on transmission in choroid neurons. 

A. indica L. Indian Aristolochia, also known as Indian birthwort, ishvara (Sanskrit), or adagam (Tamil), is a bitter climber native to India. The medicinal material consists of the rhizome, which is to resolve inflammation (India), counteract insect poison, and as an antipyretic (Philippines and Vietnam). The rhizome contains aristolochic acid, which inhibits in vitro and dose-dependent phospholipid hydrolysis by the human synovial fluid phospholipase A2, snake venom phospholipase A2, porcine pancreatic phospholipase A2, and human platelet phospholipase A2 (2). 

Kubelka, V., Altmann, F., Staudacher, E., Tretter, V., Marz, L., Hard, K., Kamerling, J.P. and Vliegenthart, F.G. (1993) Primary structure of the A-linked carbohydrate chains from honeybee venom phospholipase A2. European Journal of Biochemistry 213, 1193—1204. 

Premier, C., Mach, L., Glossl, J. and Marz, L. (1992) The antigenicity of the carbohydrate moiety of an insect glycoprotein, honey-bee (Apis mellifera) venom phospholipase A2. The role of al,3-fucosylation of the asparagine-bound IV-acetylglucosamine. Bio chemicalJournal 284, 377-380. 

Weber, A., Schroder, H., Thalberg, K. and Marz, L. (1987) Specific interactions of IgE antibodies with a carbohydrate epitope of honey-bee venom phospholipase-A2. Allergy 42, 464-470. 

Wetterwald A, Skvaril F, Muller U, Blaser K Isotypic and idiotypic characterization of anti-bee venom phospholipase A2 antibodies. Arch Allergy Appl Immunol 1985 77 195-197. 

Akdis CA, Akdis M, Blesken T, Wymann D, Alkan SS, Muller U, et al Epitope specific T-cell tolerance to phospholipase A2 in bee venom immunotherapy and recovery by IL-2 and IL-15 in vitro. J Clin Invest 1996 98 1676-1683. 

Muller U, Akdis CA, Fricker M, Akdis M, Blesken T, Bettens F, Blaser K Successful immunotherapy with T-cell epitope peptides of bee venom phospholipase A2 induces specific T-cell anergy in patients allergic to bee venom. J Allergy Clin Immunol 1998 101 747-754. 

Since predators of snakes (and humans) have to deal with snake venoms as defenses, they are included here, even though they serve in predation. Snake venoms are primarily enzymes (proteins), especially of the phospholipase A2 type, which breaks down cell membrane phospholipids hydrolytically. Other snake venoms such as cobrotoxin contain peptides with 60-70 amino acid residues. Pharmacologically, they have neurotoxic, cytotoxic, anticoagulant, and other effects. The neurotoxins, in turn, can have pre- or postsynaptic effects. Snake venoms with both neurotoxic and hemolytic effects on the heart are known as cardiotoxins. Cytotoxins attach to the cells of blood vessels and cause hemorrhage. Snake venom factors may stimulate or inhibit blood clotting. Finally, platelet-active factors can contribute to hemorrhage. 

Selected entries from Methods in Enzymology [vol, page(s)] Cobra venom phospholipase A2 Naja naja naja, 197, 359 phospholipase A2 from rat liver mitochondria, 197, 365 assay and purification of phospholipase A2 from human synovial fluid in rheumatoid arthritis, 197, 373 purification of mammalian nonpan-creatic extracellular phospholipases A2, 197, 381 spleen phospholipases A2, 197, 390 purification and characterization of cytosolic phospholipase A2 activities from canine myocardium and sheep platelets, 197, 400. 

Drugs, particularly organic bases, may release histamine from mast cells by physically displacing the amine from its storage sites. Morphine, codeine, d-tubocu-rarine, guanethidine, and radiocontrast media can release histamine from mast cells. Basic polypeptides, such as bradykinin, neurotensin, substance P, somatostatin, polymyxin B, and the anaphylatoxins resulting from complement activation, also stimulate histamine release. Venoms often contain basic polypeptides as well as the histamine-releasing enzyme phospholipase A. 

T6. The Action of Phospholipases The venom of the Eastern diamondback rattler and the Indian cobra contains phospholipase A2, which catalyzes the hydrolysis of fatty acids at the C-2 position of glycerophospholipids. The phospholipid breakdown product of this reaction is lysolecithin (lecithin is phosphatidylcholine). At high concentrations, this and other lysophospholipids act as detergents, dissolving the membranes of erythrocytes and lysing the cells. Extensive hemolysis may be life-threatening. 

The second observation which does not support the unfolded protein model is that when phospholipase A (N. naja venom) was injected into the subphase under the lipid monolayer at equilibrium with globulin, lecithin was readily attacked, as indicated by the rapid fall of surface potential (4, 5, 6). If the penetrated protein were to cover entirely the polar groups of the lipid facing the aqueous subphase (as postulated in the unfolded protein model), the lipid molecules should not be accessible to the lipolytic enzyme. 

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