Inositol Polyphosphate-5-Phosphatase 75kDa (INPP5B)

Cellular calcium signaling is controlled by the production of inositol phosphates (IPs) by phospholipase C in response to extracellular signals. The IP signaling molecules are inactivated by a family of inositol polyphosphate-5-phosphatases. INPP5B encodes the type II 5-phosphatase. The protein is localized to the cytosol and mitochondria, and associates with membranes through an isoprenyl modification near the C-terminus. Several alternatively spliced transcript variants of this gene have been described, but the full-length nature of some of these variants has not been determined.It is one of at least 3 enzymes known to catalyze the conversion of inositol-1,4,5-trisphosphate (IP3) to inositol-1,4-bisphosphate (IP2). Three enzymes with this activity were identified: a 45-kD polypeptide, a 75-kD polypeptide, and a 120-kD polypeptide.