IPPK and HIV-1 infection: However, in cells, depletion of IP6 and the related metabolite inositol (1, 3, 4, 5, 6) pentakisphosphate (IP5) via knockout (KO) of the genes encoding inositol polyphosphate multikinase (IPMK) or inositol-pentakisphosphate 2-kinase (IPPK), the cellular kinases required for IP5 and/or IP6 biogenesis, has a relatively minor effect on target cell susceptibility to HIV-1 infection (18, 19).