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, ion channel regulation. It also protects cells from TNF-induced apoptosis. . This is the function of IPPK (inositol-pentakisphosphate 2-kinase, ENSG00000127080).