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myo-Inositol 1,3,4,5,6-pentakisphosphate (Ins(1,3,4,5,6)P(5)), an inositol polyphosphate of emerging significance in cellular signalling, and its C-2 epimer scyllo-inositol pentakisphosphate (scyllo-InsP(5)) were synthesised from the same myo-inositol-based precursor. Potentiometric and NMR titrations show that both pentakisphosphates undergo a conformational ring-flip at higher pH, beginning at pH 8 for scyllo-InsP(5) and pH 9 for Ins(1,3,4,5,6)P(5). Over the physiological pH range, however, the conformation of the inositol rings and the microprotonation patterns of the phosphate groups in Ins(1,3,4,5,6)P(5) and scyllo-InsP(5) are similar. Thus, scyllo-InsP(5) should be a useful tool for identifying biologically relevant actions of Ins(1,3,4,5,6)P(5), mediated by specific binding sites, and distinguishing them from nonspecific electrostatic effects. We also demonstrate that, although scyllo-InsP(5) and Ins(1,3,4,5,6)P(5) are both hydrolysed by multiple inositol polyphosphate phosphatase (MINPP), scyllo-InsP(5) is not dephosphorylated by PTEN or phosphorylated by Ins(1,3,4,5,6)P(5) 2-kinases. This finding both reinforces the value of scyllo-InsP(5) as a biological control and shows that the axial 2-OH group of Ins(1,3,4,5,6)P(5) plays a part in substrate recognition by PTEN and the Ins(1,3,4,5,6)P(5) 2-kinases.

Original publication

DOI

10.1002/cbic.200600037

Type

Journal article

Journal

Chembiochem

Publication Date

07/2006

Volume

7

Pages

1114 - 1122

Keywords

Inositol Phosphates, Magnetic Resonance Spectroscopy, Molecular Conformation, PTEN Phosphohydrolase, Phosphoric Monoester Hydrolases, Potentiometry, Proton-Motive Force, Static Electricity, Structure-Activity Relationship, Substrate Specificity