Protein Domain : Inositol monophosphatase, lithium-sensitive IPR020552

Type	Family
Description	It has been shown that several proteins share two sequence motifs [ ]. Two of these proteins, vertebrate and plant inositol monophosphatase (), and vertebrate inositol polyphosphate 1-phosphatase ( ), are enzymes of the inositol phosphate second messenger signalling pathway, and share similar enzyme activity. Both enzymes exhibit an absolute requirement for metal ions (Mg2 is preferred), and their amino acid sequences contain a number of conserved motifs, which are also shared by several other proteins related to MPTASE (including products of fungal QaX and qutG, bacterial suhB and cysQ, and yeast hal2) [ ]. The function of the other proteins is not yet clear, but it is suggested that they may act by enhancing the synthesis or degradation of phosphorylated messenger molecules []. Structural analysis of these proteins has revealed a common core of 155 residues, which includes residues essential for metal binding and catalysis. An interesting property of the enzymes of this family is their sensitivity to Li+. The targets and mechanism of action of Li+ are unknown, but overactive inositol phosphate signalling may account for symptoms of manic depression [].An interesting property of the enzymes of this family is their sensitivity to Li+ at levels achieved in patients undergoing therapy for manicdepression. The targets and mechanism of action of Li+ are unknown, but overactive inositol phosphate signalling may account for symptoms of thedisease [ , ]. It has been proposed that these Li+-sensitive proteins could represent targets for Li+ in manic depressive disease [, , ].
Short Name	Inositol_monoPase_Li-sen