InterPro: IPR013090 Phospholipase A2, active site

Phospholipase A2 (EC:3.1.1.4) (PLA2) is a small lipolytic enzyme that releases fatty acids from the second carbon group of glycerol. It is involved in a number of physiologically important cellular processes, such as the liberation of arachidonic acid from membrane phospholipids [1]. It plays a pivotal role in the biosynthesis of prostaglandin and other mediators of inflammation. PLA2 has four to seven disulphide bonds and binds a calcium ion that is essential for activity. Within the active enzyme, the alpha amino group is involved in a conserved hydrogen-bonding network linking the N-terminal region to the active site. The side chains of two conserved residues, His and Asp, participate in the catalytic network [2].

Many PLA2's are widely distributed in snakes, lizards, bees and mammals. In mammals there are at least four forms: pancreatic, membrane-associated as well as two less well characterised forms. The venom of most snakes contains multiple forms of PLA2. Some of them are presynaptic neurotoxins which inhibit neuromuscular transmission by blocking acetylcholine release from the nerve termini.

Some of the proteins containing these active sites are allergens. Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, stings, drugs, or food) that, in most people, result in no symptoms. A nomenclature system has been established for antigens (allergens) that cause IgE-mediated atopic allergies in humans [WHO/IUIS Allergen Nomenclature Subcommittee King T.P., Hoffmann D., Loewenstein H., Marsh D.G., Platts-Mills T.A.E., Thomas W. Bull. World Health Organ. 72:797-806(1994)]. This nomenclature system is defined by a designation that is composed of the first three letters of the genus; a space; the first letter of the species name; a space and an arabic number. In the event that two species names have identical designations, they are discriminated from one another by adding one or more letters (as necessary) to each species designation.

The allergens in this family include allergens with the following designations: Api m 1.