Reaction: (1) myo-inositol hexakisphosphate + H2O = 1D-myo-inositol 1,2,4,5,6-pentakisphosphate + phosphate
(2) 1D-myo-inositol 1,2,4,5,6-pentakisphosphate + H2O = 1D-myo-inositol 1,2,5,6-tetrakisphosphate + phosphate
(3) 1D-myo-inositol 1,2,5,6-tetrakisphosphate + H2O = 1D-myo-inositol 1,2,6-trisphosphate + phosphate
(4) 1D-myo-inositol 1,2,6-trisphosphate + H2O = 1D-myo-inositol 1,2-bisphosphate + phosphate
(5) 1D-myo-inositol 1,2-bisphosphate + H2O = 1D-myo-inositol 2-phosphate + phosphate
Glossary: myo-inositol hexakisphosphate = phytate
1D-myo-inositol 1,3,4,5,6-pentakisphosphate = Ins(1,3,4,5,6)P5
1D-myo-inositol 1,3,4,5-tetrakisphosphate = Ins(1,3,4,5)P4
1D-myo-inositol 1,4,5,6-tetrakisphosphate = Ins(1,4,5,6)P4
1D-myo-inositol 1,4,5-trisphosphate = Ins(1,4,5)P3
1D-myo-inositol 2,3-bisphosphate = Ins(2,3)P2
1D-myo-inositol 2-phosphate = Ins(2)P
Other name(s): MIPP; phytase (ambiguous); 1D-myo-inositol-hexakisphosphate 5-phosphohydrolase (incorrect)
Systematic name: myo-inositol-hexakisphosphate phosphohydrolase
Comments: This ubiquitous enzyme degrades myo-inositol hexakisphosphate (phytate) to Ins(2,3)P2 and Ins(2)P. Activities have been characterized in the yeast Saccharomyces cerevisiae [2], the plant Lupinus albus [3] and the bacteria Bacillus sp. [4] and Raoultella terrigena [5]. In mammal cells Ins(2,3)P2 and Ins(2)P are the major inositol phosphate compounds found [6]. The mammal enzyme is also active on Ins(1,3,4,5,6)P5 that is dephosphorylated to Ins(1,4,5,6)P4 and Ins(1,4,5)P3, and on 2,3-bisphospho-D-glycerate (cf. EC 3.1.3.80, 2,3-bisphosphoglycerate 3-phosphatase). In addition, it acts on Ins(1,3,4,5)P4 to yield Ins(1,4,5)P3 in vitro (cf. EC 3.1.3.67, phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase) [7]. It does not hydrolyse phosphates from the 2-positions of inositol phosphates [6]. In other organisms the degradation of phytate follows different routes. (cf. EC 3.1.3.8, 3-phytase, EC 3.1.3.26, 4-phytase, and EC 3.1.3.72, 5-phytase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 116958-30-6
References:
1. Craxton, A., Caffrey, J.J., Burkhart, W., Safrany, S.T. and Shears, S.B. Molecular cloning and expression of a rat hepatic multiple inositol polyphosphate phosphatase. Biochem. J. 328 (1997) 75-81. [PMID: 9359836]
2. Greiner, R., Alminger, M.L. and Carlsson, N.G. Stereospecificity of myo-inositol hexakisphosphate dephosphorylation by a phytate-degrading enzyme of baker's yeast. J. Agric. Food Chem. 49 (2001) 2228-2233. [PMID: 11368581]
3. Greiner, R., Larsson Alminger, M., Carlsson, N.G., Muzquiz, M., Burbano, C., Cuadrado, C., Pedrosa, M.M. and Goyoaga, C. Pathway of dephosphorylation of myo-inositol hexakisphosphate by phytases of legume seeds. J. Agric. Food Chem. 50 (2002) 6865-6870. [PMID: 12405789]
4. Greiner, R., Farouk, A., Alminger, M.L. and Carlsson, N.G. The pathway of dephosphorylation of myo-inositol hexakisphosphate by phytate-degrading enzymes of different Bacillus spp. Can. J. Microbiol. 48 (2002) 986-994. [PMID: 12556126]
5. Greiner, R. and Carlsson, N.G. myo-Inositol phosphate isomers generated by the action of a phytate-degrading enzyme from Klebsiella terrigena on phytate. Can. J. Microbiol. 52 (2006) 759-768. [PMID: 16917535]
6. Nguyen Trung, M., Kieninger, S., Fandi, Z., Qiu, D., Liu, G., Mehendale, N.K., Saiardi, A., Jessen, H., Keller, B. and Fiedler, D. Stable isotopomers of myo-inositol uncover a complex MINPP1-dependent inositol phosphate network. ACS Cent. Sci. 8 (2022) 1683-1694. [PMID: 36589890]
7. Yu, J., Leibiger, B., Yang, S.N., Shears, S.B., Leibiger, I.B., Berggren, P.O. and Barker, C.J. Multiple inositol polyphosphate phosphatase compartmentalization separates inositol phosphate metabolism from inositol lipid signaling. Biomolecules 13 (2023) . [PMID: 37371464]