Diphospho-myo-inositol phosphates from Dictyostelium identified as d-6-diphospho-myo-inositol pentakisphosphate and d-5,6-bisdiphospho-myo-inositol tetrakisphosphate

Abstract

Two diphospho-myo-inositol phosphates from Dictyostelium were recently investigated by two-dimensional ¹H/³¹P NMR analysis and assigned to be either d-4-diphospho-myo-inositol pentakisphosphate (d-4-PP-InsP₅) and d-4,5-bisdiphospho-myo-inositol tetrakisphosphate (d-4,5-bis-PP-InsP₄) or their corresponding enantiomers d-6-PP-InsP₅ and d-5,6-bis-PP-InsP₄. In the present study the naturally occurring enantiomers were identified by using defined synthetic PP-InsP₅ isomers as substrates for a partially purified PP-InsP₅ 5-kinase from Dictyostelium. This enzyme specifically phosphorylates the naturally occurring PP-InsP₅ and the synthetic d-6-PP-InsP₅, leading to d-5,6-bis-PP-InsP₄. In contrast, neither d-4-PP-InsP₅ nor d-1-PP-InsP₅ or d-3-PP-InsP₅ are converted by the enzyme.