Phospholipase C gamma 1 is a tryosine kinase substrate for many receptor and nonreceptor tyrosine kinases. Activation of the enzyme produces two second messenger molecules, inositol 1,4,5-triphosphate and diacylglycerol, which provoke the mobilization of intracellular Ca2+ and activation of protein kinase C. Although the mammalian genome encodes 10 known phosphoinositide specific PLCs, only the gamma 1 and gamma 2 isoforms are regulated by tyrosine kinase activity. PLC beta isoform activity is controlled by heterotrimeric G protein coupled receptors, while the mechanism of regulation of PLC gamma activity is unknown.