PI3K (phosphatidylinositol 3 kinase)

PI3K, which phosphorylates the inositol ring of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PI-4P) and phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) at the 3' hydroxyl position, is composed of 85 kDa regulatory and 110 kDa catalytic subunits. The 85 kDa subunit (p85 PI3K) lacks PI 3-kinase activity and functions as an adaptor, coupling the 110 kDa subunit (p110 PI3K) to activated protein tyrosine kinase.