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 enantiome rs were identified by using defined synthetic PP-InsP(5) isomers as su bstrates for a partially purified PP-InsP(5) 5-kinase from Dictyosteli um. 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-Ins P(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.