Determination of neo- and d-chiro-Inositol Hexakisphosphate in Soils by Solution 31P NMR Spectroscopy

The inositol phosphates are an abundant but poorly understood group of organic phosphorus compounds found widely in the environment. Four stereoisomers of inositol hexakisphosphate (IP6) occur, although for three of these (scyllo, flea, and D-chiro) the origins, dynamics, and biological function remain unknown, due in large part to analytical limitations in their measurement in environmental samples. We synthesized authentic neo- and n-chiro-IP6 and used them to identify signals from these compounds in three soils from the Falkland Islands. Both compounds resisted hypobromite oxidation and gave quantifiable P-31 NMR signals at delta = 6.67 ppm (equatorial phosphate groups of the 4-equatorial/2-axial conformer of neo-IP6) and delta = 6.48 ppm (equatorial phosphate groups of the 2-equatorial/4-axial conformer of D-chiro-IP6) in soil extracts. Inositol hexakisphosphate accounted for 46-54% of the soil organic phosphorus, of which the four stereoisomers constituted, on average, 55.9% (myo), 32.8% (scyllo), 6.1% (neo), and 5.2% (n-chiro). Reappraisal of the literature based on the new signal assignments revealed that neo- and D-chiro-IP6 occur widely in both terrestrial and aquatic ecosystems. These results confirm that the inositol phosphates can constitute a considerable fraction of the organic phosphorus in soils and reveal the prevalence of neo- and D-chiro-IP6 in the environment. The hypobromite oxidation and solution P-31 NMR spectroscopy procedure allows the simultaneous quantification of all four IP6 stereoisomers in environmental samples and provides a platform for research into the origins and ecological significance of these enigmatic compounds

Simple synthesis of 32P-labelled inositol hexakisphosphates for study of phosphate transformations

In many soils inositol hexakisphosphate in its various forms is as abundant as inorganic phosphate. The organismal and geochemical processes that exchange phosphate between inositol hexakisphosphate and other pools of soil phosphate are poorly defined, as are the organisms and enzymes involved. We rationalized that simple enzymic synthesis of inositol hexakisphosphate labeled with 32P would greatly enable study of transformation of soil inositol phosphates when combined with robust HPLC separations of different inositol phosphates

On the contribution of stereochemistry to human ITPK1 specificity: Ins(1,4,5,6)P4 is not a physiologic substrate

Ins(1,4,5,6)P4, a biologically active cell constituent, was recently advocated as a substrate of human Ins(3,4,5,6)P4 1-kinase (hITPK1), because stereochemical factors were believed relatively unimportant to specificity [Miller, G.J. Wilson, M.P. Majerus, P.W. and Hurley, J.H. (2005) Specificity determinants in inositol polyphosphate synthesis: crystal structure of inositol 1,3,4-triphosphate 5/6-kinase. Mol. Cell. 18, 201-212]. Contrarily, we provide three examples of hITPK1 stereospecificity. hITPK1 phosphorylates only the 1-hydroxyl of both Ins(3,5,6)P3 and the meso-compound, Ins(4,5,6)P3. Moreover, hITPK1 has >13,000-fold preference for Ins(3,4,5,6)P4 over its enantiomer, Ins(1,4,5,6)P4. The biological significance of hITPK1 being stereospecific, and not physiologically phosphorylating Ins(1,4,5,6)P4, is reinforced by our demonstrating that Ins(1,4,5,6)P4 is phosphorylated (K(m) = 0.18 microM) by inositolphosphate-multikinase.info:eu-repo/semantics/publishe