Reference work entry
Phosphoinositide 3-kinase, commonly abbreviated PI3K, is one of the most well-studied enzymes in the field of signal transduction (Fruman et al. 1998; Vanhaesebroeck et al. 2010). PI3K actually refers to a family of enzymes encoded by eight genes in mammals. Orthologs of one or more PI3K genes exist in all animals as well as in yeast. These enzymes share the ability to phosphorylate the 3′-hydroxyl of the inositol head group of phosphatidylinositol (PtdIns), generating the lipid PtdIns-3-P (Fig. 1). Some members of the PI3K family can act on phosphoinositides, which are phosphorylated derivatives of PtdIns (such as PtdIns-4,5-P 2). Therefore, the family is properly referred to as phosphoinositide 3-kinases rather than simply phosphatidylinositol 3-kinases. The products of PI3Ks, generally termed 3-phosphorylated inositides (3-PIs), serve as membrane...
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