| Description | Phosphatidylinositol 3-kinase (PI3K) ( ) is an enzyme that phosphorylates phosphoinositides on the 3-hydroxyl group of the inositol ring. The role of the accessory domain of phosphoinositide 3-kinase (PI3-kinase) is unclear. It may be involved in substrate presentation [ ].PI3Ks fall into three classes based on their primary structure and substrate specificity. The class I PI3Ks can use phosphatidylinositol 4,5-bisphosphate (PIP2) as a substrate to generate the second messenger PIP3 and act as transducers downstream of tyrosine kinase receptors and G protein-coupled receptors. PI3Ks are involved in a large number of fundamental cellular processes, including apoptosis, proliferation, cell motility, and adhesion. The 3-phosphorylated phospholipids generated by PI3Ks act as membrane tethers for proteins such as protein kinase B (PKB) and phospholipid-dependent kinase 1 (PDK1). These are important components of the molecular mechanisms of diseases such as diabetes, cancer, and chronic inflammation. The class I isozymes are subdivided into classes IA and IB, with each subtype having a different regulatory subunit. The class IA enzymes (alpha, beta, and delta) have a p85 regulatory subunit containing two SH2 domains, which are essential for their activation by tyrosine kinase receptors. The class IB PI3K gamma has a p101 subunit, which is required for maximal G-beta-gamma-stimulated formation of PIP3 [ ]. | Name | Phosphoinositide 3-kinase, accessory (PIK) domain superfamily |
| Short Name | PI3K_accessory_sf | Type | Homologous_superfamily |
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