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Description

Phosphatidylinositol 4-kinase beta (UniProt: Q9UBF8, also known as EC:2.7.1.67, PI4K-beta, PI4Kbeta, PtdIns 4-kinase beta, NPIK, PI4K92, PI4KIII) is encoded by the PI4KB (also known as PIK4CB) gene (Gene ID: 5298) in human. A group of four enzymes make up the mammalian phosphatidylinositol (PI) 4-kinase family are divided into two groups based on primary sequence and biochemical properties: consisting of type II (PI4KII and PI4KII&beta,) and the type III (PI4KIII and PI4KIII&beta,) isozymes. They all catalyze the phosphorylation of phosphatidylinositol (PI) at the D4 position of the inositol head-group to synthesize phosphatidylinositol 4-phosphate (PI4P) that serves as an essential precursor to produce PIP2 and PIP3. PI4-kinase b is a type III peripheral membrane protein that is present in the outer membrane of mitochondria and membranes of the rough endoplasmic reticulum. It phosphorylates phosphatidylinositol (PI) in the first committed step in the production of the second messenger inositol-1,4,5,-trisphosphate (PIP). It also regulates Golgi disintegration/reorganization during mitosis, possibly via its phosphorylation and is involved in Golgi-to-plasma membrane trafficking. PI4-kinase b is shown to be critical for glucose-induced insulin secretion due to its capacity to regulate the release of secretory granules. In addition, it inhibits the insulin-stimulated translocation of glucose transporter-4 in adipocytes through its interaction with neuronal calcium sensor. (Ref.: Chalupska, D., et al. (2019). Sci. Rep. 9, article 567, Clyton, EL., et al. (2013). Prog. Lipid Res. 52(3), 294-304).