Class I Phosphoinositide 3-kinases (PI3Ks) are heterodimeric proteins, each having a catalytic subunit of 110-120 kDa and an associated regulatory subunit. PI3Ks alpha, beta and delta share a common regulatory p85 subunit, PI3K gamma has a p101 regulatory subunit. All the class I PI3Ks are able to phosphorylate PtdIns, PtdIns-4-P, or PtdIns-4,5-P2 (PIP2) on the free 3-position, and have a strong preference for PIP2.They are activated
by receptor tyrosine kinases and by Ras and Rho family GTPases.
phosphatidylinositol-4,5-bisphosphate 3-kinase activity of PI3K alpha, beta, gamma [cytosol]