title: Stereospecificity of myo-inositol hexakisphosphate dephosphorylation by a phytate-degrading enzyme of Escherichia coli.
abstract: Using a combination of high-performance ion chromatography analysis and kinetic studies, the stereospecificity of myo-inositol hexakisphosphate dephosphorylation by the phytate-degrading enzyme P2 of Escherichia coli was established. High-performance ion chromatography revealed that the phytate-degrading enzyme P2 of E. coli degrades myo-inositol hexakisphosphate by stepwise dephosphorylation via D/L-Ins(1,2,3,4,5)P(5), D/L-Ins(2,3,4,5)P(4), D/L-Ins(2,4,5)P(3) or D/L-Ins(1,2,4)P(3), D/L-Ins(1,2)P(2) or Ins(2, 5)P(2) or D/L-Ins(4,5)P(2) to finally Ins(2)P or Ins(5)P. Kinetic parameters for myo-inositol pentakisphosphate hydrolysis by E. coli and wheat phytase, respectively, showed that the myo-inositol pentakisphosphate intermediate produced either by the phytate-degrading enzyme of wheat or E. coli are not identical. The absolute configuration of the myo-inositol pentakisphosphate isomer produced by the E. coli enzyme was determined by taking into consideration that wheat phytase produces predominantly the D-Ins(1, 2,3,5,6)P(5) isomer (Lim, P.E., Tate, M.E., 1973. The phytases: II. Properties of phytase fraction F(1) and F(2) from wheat bran and the myo-inositol phosphates produced by fraction F(2). Biochim. Biophys. Acta 302, 326-328). The data demonstrate that the phytate-degrading enzyme P2 of E. coli dephosphorylates myo-inositol hexakisphosphate in a stereospecific way by sequential removal of phosphate groups via D-Ins(1,2,3,4,5)P(5), D-Ins(2,3,4,5)P(4), D-Ins(2,4,5)P(3), Ins(2,5)P(2) to finally Ins(2)P (notation 6/1/3/4/5).
authors.affiliation: Centre for Molecular Biology, Federal Research Centre for Nutrition, Haid-und-Neu-Strasse 9, D-76131, Karlsruhe, Germany. ralf.greiner@bfe.uni-karlsruhe.de
authors.forename: R
authors.initials: R
authors.lastname: Greiner
authors.forename: N
authors.initials: N
authors.lastname: Carlsson
authors.forename: M L
authors.initials: ML
authors.lastname: Alminger
mesh_terms: D010832:6-Phytase / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004926:Escherichia coli / Q000201:enzymology*; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D007536:Isomerism; D007700:Kinetics; D008968:Molecular Conformation; D010766:Phosphorylation; D010833:Phytic Acid / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D007295:Inositol Phosphates; C013571:inositol pentaphosphate; D010833:Phytic Acid; C062616:inositol 2,4,5-trisphosphate; D010832:6-Phytase