Phosphoinositide-specific phospholipase C (PLC) plays a crucial role in the initiation of receptor mediated signal transduction through the generation of the two second messengers, inositol 1,4,5-triphosphate and diacylglycerol from phosphatidylinositol 4,5-bisphosphate. There are many mammalian PLC isozymes, including PLC beta1, PLC beta2, PLC beta3, PLC beta4, PLC gamma 1, PLC gamma 2, PLC delta1,PLC delta2 and PLC E). PLC betas are the only PLC isforms that are regulated by G protein subunits and are activated by a heterotrimeric GTP-binding protein linked to various cell surface receptors. Two alternatively spliced forms (1,181 and 1,166 amino acids) of PLC beta2 are generated in hematopoietic cells that differ in the carboxyl-terminal sequence implicated in interaction of PLC beta enzymes with Galphaq.The pleckstrin homology domain of PLC beta2 is required for its targeting to the membrane and for substrate hydrolysis and its linker region exerts an inhibitory efect on basal PLC beta2 activity. PLC beta2 plays a major role in platelet activation and is mainly expressed in the periphery of the islet and acinar cells in rat pancreas.