Synthetic inositol 1,3,4,5-tetrakisphosphate analogues.

Inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4] analogues were synthesized and their effects on [3H]Ins(1,3,4,5)P4 5-phosphatase, [3H]Ins(1,3,4,5)P4 3-phosphatase and [3H]inositol 1,4,5-trisphosphate [3H]Ins(1,4,5)P3] 5-phosphatase activities were examined. The Ins(1,3,4,5)P4 analogue with the aminobenzoyl group at the 2-position of Ins(1,3,4,5)P4 inhibited the hydrolysis of 5-phosphate of [3H]Ins(1,3,4,5)P4 catalysed by erythrocyte ghosts, with a lower Ki value than seen with Ins(1,3,4,5)P4, whereas the analogue with the aminocyclohexanecarbonyl group at the same position had a higher Ki value. The Ins(1,4,5)P3 analogues that we had previously synthesized were also capable of inhibiting this process, with the same tendency as Ins(1,3,4,5)P4 analogues. Such differences in the potency among Ins(1,3,4,5)P4 and Ins(1,4,5)P3 analogues were applicable to other phosphatase activities, namely [3H]Ins(1,3,4,5)P4 3-phosphatase and [3H]Ins(1,4,5)P3 5-phosphatase. These results suggest that the active sites of these enzymes may catalyse the dephosphorylation in a similar fashion.