OBSOLETE. Catalysis of the reaction: ATP + 1D-myo-inositol hexakisphosphate = ADP + 4-diphospho-1D-myo-inositol (1,2,3,5,6)pentakisphosphate, and ATP + 1D-myo-inositol hexakisphosphate = ADP + 6-diphospho-1D-myo-inositol (1,2,3,4,5)pentakisphosphate.