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Catalytic domain of inositol polyphosphate 5-phosphatases Inositol polyphosphate 5-phosphatases (5-phosphatases) are signal-modifying enzymes, which hydrolyze the 5-phosphate from the inositol ring of specific 5-position phosphorylated phosphoinositides (PIs) and inositol phosphates (IPs), such as PI(4,5)P2, PI(3,4,5)P3, PI(3,5)P2, I(1,4,5)P3, and I(1,3,4,5)P4. These enzymes are Mg2+-dependent, and belong to the large EEP (exonuclease/endonuclease/phosphatase) superfamily that contains functionally diverse enzymes that share a common catalytic mechanism of cleaving phosphodiester bonds. In addition to this INPP5c domain, 5-phosphatases often contain additional domains and motifs, such as the SH2 domain, the Sac-1 domain, the proline-rich domain (PRD), CAAX, RhoGAP (RhoGTPase-activating protein), and SKICH [SKIP (skeletal muscle- and kidney-enriched inositol phosphatase) carboxyl homology] domains, that are important for protein-protein interactions and/or for the subcellular localization of these enzymes. 5-phosphatases incorporate into large signaling complexes, and regulate diverse cellular processes including postsynaptic vesicular trafficking, insulin signaling, cell growth and survival, and endocytosis. Loss or gain of function of 5-phosphatases is implicated in certain human diseases. This family also contains a functionally unrelated nitric oxide transport protein, Cimex lectularius (bedbug) nitrophorin, which catalyzes a heme-assisted S-nitrosation of a proximal thiolate; the heme however binds at a site distinct from the active site of the 5-phosphatases. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",