Inositol hexakisphosphate kinase

Inositol-hexakisphosphate kinase (EC 2.7.4.21, ATP:1D-myo-inositol-hexakisphosphate phosphotransferase) is an enzyme with systematic name ATP:1D-myo-inositol-hexakisphosphate 5-phosphotransferase. This enzyme catalyses the following chemical reaction

(1) ATP + 1D-myo-inositol hexakisphosphate ⇌ ADP + 1D-myo-inositol 5-diphosphate 1,2,3,4,6-pentakisphosphate(2) ATP + 1D-myo-inositol 1,3,4,5,6-pentakisphosphate ⇌ ADP + 1D-myo-inositol diphosphate tetrakisphosphate (isomeric configuration unknown)

Three mammalian isoforms are known to exist.