Use of phosphorofluoridate analogues of D-myo-inositol 1,4,5-trisphosphateto assess the involvement of ionic interactions in its recognition by the receptor and metabolising enzymes

D-myo-Inositol 1,4,5 trisphosphate [Ins(1,4,5)P-3] analogues fluoridated at 4- or 5-phosphate or both were analysed to assess the involvement of ionic interactions between the phosphates of Ins(1,4,5)P-3 and the proteins that recognize it, such as metabolic enzymes and the InsP(3) receptor. These an alogues were effective in inhibiting type I Ins(1,4,5)P-3 5-phosphatase act ivity with much thr same potency as Ins(1,4,5)P-3, although the enzyme show ed a lower K-m value as pH values increased. In contrast, the analogues wer e less potent ligands than Ins(1,4,5)P-3 in both the assay of [H-3]Ins(1,4, 5)P-3 binding to the receptors and the phosphorylation of [H-3]Ins(1,4,5)P- 3 catalysed by Ins(1,4,5)P-3 3-kinase. These results suggest that ionic int eractions with the dianionic 4 and 5-phosphates of Ins(1,4,5)P-3 are involv ed in recognition by the receptor and the kinase, but not by the phosphatas e. CELL SIGNAL 11;2:117-125, 1999. (C) 1998 Elsevier Science Inc.