Inositol-tetrakisphosphate 1-kinase (ITPK1) can phosphorylate various inositol polyphosphate such as Ins(3,4,5,6)P4 or Ins(1,3,4)P3. Phosphorylates Ins(3,4,5,6)P4 at position 1 to form Ins(1,3,4,5,6)P5 which may play a regulatory function. It may also act as an isomerase. This entry represents the preATP-grasp domain [1].

1: Specificity determinants in inositol polyphosphate synthesis: crystal structure of inositol 1,3,4-trisphosphate 5/6-kinase. Miller GJ, Wilson MP, Majerus PW, Hurley JH; Mol Cell. 2005;18:201-212. PMID:15837423