{PDOC50007} {PS50007; PIPLC_X_DOMAIN} {PS50008; PIPLC_Y_DOMAIN} {BEGIN} ********************************************************** * Phosphatidylinositol-specific phospholipase C profiles * ********************************************************** Phosphatidylinositol-specific phospholipase C (EC 3.1.4.11), an eukaryotic intracellular enzyme, plays an important role in signal transduction processes [1]. It catalyzes the hydrolysis of 1-phosphatidyl-D-myo-inositol-4,5- diphosphate into the second messenger molecules diacylglycerol and inositol- 1,4,5-triphosphate. This catalytic process is tightly regulated by reversible phosphorylation and binding of regulatory proteins [2 to 4]. In mammals, there are at least 6 different isoforms of PI-PLC, they differ in their domain structure, their regulation, and their tissue distribution. Lower eukaryotes also possess multiple isoforms of PI-PLC. All eukaryotic PI-PLCs contain two regions of homology, sometimes referred to as 'X-box' and 'Y-box'. The order of these two regions is always the same (NH2-X-Y-COOH), but the spacing is variable. In most isoforms, the distance between these two regions is only 50-100 residues but in the gamma isoforms one PH domain, two SH2 domains, and one SH3 domain are inserted between the two PLC-specific domains. The two conserved regions have been shown to be important for the catalytic activity. At the C-terminal of the Y-box, there is a C2 domain (see ) possibly involved in Ca-dependent membrane attachment. By profile analysis, we could show that sequences with significant similarity to the X-box domain occur also in prokaryotic and trypanosome PI-specific phospholipases C. Apart from this region, the prokaryotic enzymes show no similarity to their eukaryotic counterparts. We developed two profiles, one covering the X-box, the other the Y-box. -Sequences known to belong to this class detected by the X-box profile: ALL. known eukaryotic and prokaryotic PI-PLCs. -Other sequence(s) detected in Swiss-Prot: 1. -Sequences known to belong to this class detected by the Y-box profile: ALL. known eukaryotic PI-PLCs. -Other sequence(s) detected in Swiss-Prot: NONE. -Last update: July 2003 / Text revised. [ 1] Meldrum E., Parker P.J., Carozzi A. "The PtdIns-PLC superfamily and signal transduction." Biochim. Biophys. Acta 1092:49-71(1991). PubMed=1849017 [ 2] Rhee S.G., Choi K.D. "Multiple forms of phospholipase C isozymes and their activation mechanisms." Adv. Second Messenger Phosphoprotein Res. 26:35-61(1992). PubMed=1419362 [ 3] Rhee S.G., Choi K.D. "Regulation of inositol phospholipid-specific phospholipase C isozymes." J. Biol. Chem. 267:12393-12396(1992). PubMed=1319994 [ 4] Sternweis P.C., Smrcka A.V. "Regulation of phospholipase C by G proteins." Trends Biochem. Sci. 17:502-506(1992). PubMed=1335185 -------------------------------------------------------------------------------- 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}