Phospholipases A

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... 

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. 

Phospholipases A, A2, C and D PLN Peripheral lymph node PLNHEV Peripheral lymph node HEV... 

Bernard P, Scior T, Didier B, Hibert M, Berthon JY. Ethnopharmacology and bioinfor-matic combination for leads discovery application to phospholipase A(2) inhibitors. Phytochemistry 2001 58 865-874 ... 

Wichmann, O. and Schultz, C. (2001). FRET probes to monitor phospholipase A(2) activity. Chem. Commun. 2500-2501. 

Hendrickson, H. S., Hendrickson, E. K., Johnson, I. D. and Farber, S. A. (1999). Intramolecularly quenched BODIPY-labeled phospholipid analogs in phospholipase A(2) and platelet-activating factor acetylhydrolase assays and in vivo fluorescence imaging. Anal. Biochem. 276, 27-35. 

Rose, T. M. and Prestwich, G. D. (2006). Fluorogenic phospholipids as head group-selective reporters of phospholipase A activity. ACS Chem. Biol. 1, 83-92. 

Wichmann, O., Gelb, M. H. and Schultz, C. (2007). Probing Phospholipase A(2) with Fluorescent Phospholipid Substrates. Chembiochem 8, 1555-1569. 

Wu Z et al (2009) The use of phospholipase A(2) to prepare acellular porcine corneal stroma as a tissue engineering scaffold. Biomaterials 30(21) 3513-3522... 

PLA phospholipase A SCAD short chain acyl-CoA dehydrogenase... 

Topical corticosteroids (Table 16-1) may halt synthesis and mitosis of DNA in epidermal cells and appear to inhibit phospholipase A, lowering the amounts of arachidonic acid, prostaglandins, and leukotrienes in the skin. These effects, coupled with local vasoconstriction, reduce erythema, pruritus, and scaling. As antipsoriatic agents, they are best used adjunc-tively with a product that specifically functions to normalize epidermal hyperproliferation. 

Figure 6.5. Specificity of action of phospholipases. A phospholipid is shown, and the specificity of action of phospholipases A, A 2, C and D is indicated.

Okada S, Jelinek R, Charych D (1999) Induced color change of conjugated polymeric vesicles by interfacial catalysis of phospholipase A(2). Angew Chem Int Ed 38 655-659... 

Anthonsen, M.W., Stengel, D., Hourton, D., Ninio, E., Johansen, B., 2000, Mildly oxidized LDL induces expression of group 11a secretory phospholipase A(2) in human monocyte-derived macrophages, Arterioscler Thromb Vase Biol, 20 1276-1282. 

Figure 11.30 Mechanisms of regulation of phospholipase A2. In all these processes described above, it is phospholipase A that carries out the hydrolysis of membrane phospholipid. Cytokines are local hormones produced by immune cells, T-lymphocytes and macrophages (Chapter 17). Other factors relate to shear stress in endothelial cells and those that stimulate release of granules from mast cells. Eicosanoids are present in the granules and they must be re-synthesised after degranulation in the mast cells. Here the enzymes described above must be present in mast cells.

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