Inositol polyphosphate-5-phosphatase B (INPP5B)

Inositol polyphosphate-5-phosphatase B (INPP5B) is an enzyme encoded by the INPP5B gene, part of a family of 5-phosphatases that regulate calcium signaling by hydrolyzing the 5-phosphate group from inositol phosphates and phosphoinositides[3][4][1]. The protein is localized to the cytosol and mitochondria and associates with cell membranes through an isoprenylated C-terminus[4][3]. INPP5B plays roles in the endocytic pathway and the early secretory pathway, interacting with Rab GTPase proteins to help mediate ER-Golgi trafficking and vesicular transport[2][1]. It shares similarity and functional overlap with the Lowe syndrome protein OCRL1 and can compensate for its loss in knockout models[2]. Cellular studies suggest a distinct involvement in retrograde trafficking and response to vesicular transport inhibitors such as brefeldin A[2]. There is no specific major disease directly associated with INPP5B, although it is linked to rare genetic disorders and is known to be hijacked by pathogens such as *Yersinia pseudotuberculosis* during infection[1][4].

Other names

Type II inositol 1,4,5-trisphosphate 5-phosphataseOCRL25PTase75 kDa inositol polyphosphate-5-phosphatasePhosphoinositide 5-phosphataseINPP5B

Competitive inhibition of the phosphatase active site by substrate analogs or surrogates (e.g., synthetic polyphosphates)\nModulation of calcium signaling through hydrolysis of IP3 and phosphoinositides