| Description | This group of proteins is comprised entirely of phosphatidylinositol 3- and phosphatidylinositol 4-kinases. Phosphatidylinositol 3-kinase (PI3-kinase) [ ] 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) [] 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 [, ]. 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. | Name | Phosphatidylinositol kinase |
| Short Name | PI_Kinase | Type | Family |
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