<p>Phosphatidylinositol 3-kinase (PI3-kinase) (<db_xref db="EC" dbkey="2.7.1.137"/>) 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 [<cite idref="PUB00005173"/>].</p>