What is the function of phosphokinase?

phosphatidylinositol (PI) is the name given to the lipid molecule whose head group consists of three hydroxylated inositols. Its major function is to regulate membrane traffic by serving as a phospho-donor.

PI is the source of the second messenger DAG (diacylglycerol). It is produced by phosphorylation of diacylglycerol in a reaction catalyzed by phosphatidylinositol kinase (PIK) to form PI 3-phosphate. PI 3-phosphate is then converted into PI 4, 5, and 6 phosphate derivatives. Inositol-containing lipids are components of the Phosphokinase membranes of the Golgi apparatus, mitochondria, lysosomes, and endosomes. The inositol ring of PI may also participate in the recruitment of effectors of the insulin signaling pathway to specific subcellular sites. PI is also involved in vesicular trafficking by direct interaction with coat protein complex I (COPI), clathrin, and adaptor proteins, and through the interaction with phospholipids. It regulates the morphology and activity of the actin cytoskeleton and membrane fission and fusion events. It is also involved in the process of exocytosis.