Phosphatidylinositol kinase (IPR015433)

Short name: PI_Kinase

Overlapping homologous superfamilies


Family relationships


This group of proteins is comprised entirely of phosphatidylinositol 3- and phosphatidylinositol 4-kinases. Phosphatidylinositol 3-kinase (PI3-kinase) [PMID: 1322797] is an enzyme that phosphorylates phosphoinositides on the 3-hydroxyl group of the inositol ring. The three products of PI3-kinase, PI-3-P, PI-3,4-P(2) and PI-3,4,5-P(3), function as secondary messengers in cell signalling. Phosphatidylinositol 4-kinase (PI4-kinase) [PMID: 8194527] acts on phosphatidylinositol (PI) in the first committed step of the production of the secondary messenger inositol-1,4,5-trisphosphate. The PI3- and PI4-kinases share a well-conserved domain at their C-terminal section, which is distantly related to the catalytic domain of protein kinases [PMID: 8387896, PMID: 12151228]. The catalytic domain of PI3K has a bilobal structure with a small N-terminal lobe and a large C-terminal lobe; this structure is often found in other ATP-dependent kinases. The core of this catalytic domain is the most conserved region of the PI3Ks. The ATP cofactor binds in the crevice formed by the N-and C-terminal lobes, a loop between two strands provides a hydrophobic pocket for binding of the adenine moiety, and a lysine residue interacts with the alpha-phosphate. In contrast to other protein kinases, the PI3K loop interacts with the phosphates of the ATP, known as the glycine-rich or P-loop, contains no glycine residues. Instead, contact with the ATP -phosphate is maintained through the side chain of a conserved serine residue.

GO terms

Biological Process

GO:0046854 phosphatidylinositol phosphorylation
GO:0048015 phosphatidylinositol-mediated signaling

Molecular Function

No terms assigned in this category.

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.