{PDOC00109} {PS00118; PA2_HIS} {PS00119; PA2_ASP} {BEGIN} ******************************************** * Phospholipase A2 active sites signatures * ******************************************** Phospholipase A2 (EC 3.1.1.4) (PA2) [1,2] is an enzyme which releases fatty acids from the second carbon group of glycerol. PA2's are small and rigid proteins of 120 amino-acid residues that have four to seven disulfide bonds. PA2 binds a calcium ion which is required for activity. The side chains of two conserved residues, a histidine and an aspartic acid, participate in a 'catalytic network'. Many PA2's have been sequenced from snakes, lizards, bees and mammals. In the latter, there are at least four forms: pancreatic, membrane-associated as well as two less characterized forms. The venom of most snakes contains multiple forms of PA2. Some of them are presynaptic neurotoxins which inhibit neuromuscular transmission by blocking acetylcholine release from the nerve termini. We derived two different signature patterns for PA2's. The first is centered on the active site histidine and contains three cysteines involved in disulfide bonds. The second is centered on the active site aspartic acid and also contains three cysteines involved in disulfide bonds. -Consensus pattern: C-C-{P}-x-H-{LGY}-x-C [H is the active site residue] -Sequences known to belong to this class detected by the pattern: ALL known functional PA2's. However, this pattern will not detect some snake toxins homologous with PA2 but which have lost their catalytic activity as well as otoconin-22, a Xenopus protein from the aragonitic otoconia which is also unlikely to be enzymatically active. -Other sequence(s) detected in Swiss-Prot: 15. -Consensus pattern: [LIVMA]-C-{LIVMFYWPCST}-C-D-{GS}-{G}-{N}-x-{QS}-C [D is the active site residue] -Sequences known to belong to this class detected by the pattern: the majority of functional and non-functional PA2's. Undetected sequences are bee PA2, gila monster PA2's, PA2 PL-X from habu and PA2 PA-5 from mulga. -Other sequence(s) detected in Swiss-Prot: 13. -Last update: April 2006 / Pattern revised. [ 1] Davidson F.F., Dennis E.A. "Evolutionary relationships and implications for the regulation of phospholipase A2 from snake venom to human secreted forms." J. Mol. Evol. 31:228-238(1990). PubMed=2120459 [ 2] Gomez F., Vandermeers A., Vandermeers-Piret M.-C., Herzog R., Rathe J., Stievenart M., Winand J., Christophe J. "Purification and characterization of five variants of phospholipase A2 and complete primary structure of the main phospholipase A2 variant in Heloderma suspectum (Gila monster) venom." Eur. J. Biochem. 186:23-33(1989). PubMed=2480893 -------------------------------------------------------------------------------- PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) License, see https://prosite.expasy.org/prosite_license.html -------------------------------------------------------------------------------- {END}