Inositol Hexaphosphate Kinase 3 (IHPK3)

Inositol Hexaphosphate Kinase 3 belongs to the inositol phosphokinase (IPK) family. This protein is likely responsible for the conversion of inositol hexakisphosphate (InsP6) to diphosphoinositol pentakisphosphate (InsP7/PP-InsP5). It may also convert 1,3,4,5,6-pentakisphosphate (InsP5) to PP-InsP4. Alternative splicing results in multiple transcript variants encoding the same protein. The deduced 410-amino acid protein is 51% and 45% identical to mouse Ihpk1 and human IHPK2, respectively. The acidic protein contains fewer lysine and arginine residues than the other IHPKs, but retains an 18-residue catalytic site. Confocal microscopy demonstrated that mouse Ihpk1 is present in both the nucleus and the cytoplasm, whereas IHPK2 is almost exclusively nuclear and IHPK3 is predominantly cytoplasmic.