Phosphorylates Ins(1,3,4,5,6)P5 at position 2 to form Ins(1,2,3,4,5,6)P6 (InsP6 or phytate). InsP6 is involved in many processes such as mRNA export, non-homologous end-joining, endocytosis and ion channel regulation. InsP6 also acts as a key regulator of left-right asymmetry in embryo, probably by regulating asymmetric Ca(2+) during left-right specification. 1D-myo-inositol 1,3,4,5,6-pentakisphosphate + ATP = 1D-myo-inositol hexakisphosphate + ADP + H(+) Expressed both maternally and zygotically. Expressed in cleavage-stage embryos. Ubiquitously distributed throughout blastula stages of embryogenesis. At the onset of gastrulation, it is enriched in cells around the blastoderm margin. At shield stage, expression is detected in the deep involuted cells that contribute to mesendoderm. During mid and late gastrula stages, it is strongly expressed in axial mesendoderm. However, it is not present in the nascent tailbud at yolk plug closure (YPC) stage. Expression in axial mesendoderm is reduced at the 2 somite stage (SS). At 6 SS, it is expressed in cells surrounding Kupffer's vesicle, but apparently not within. By 10 SS, it is no longer detected as a specific signal above background. The EXKPK motif is conserved in inositol-pentakisphosphate 2-kinases of both family 1 and 2. Belongs to the IPK1 type 2 family.