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

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