Fig. 1.

Schematic depicting known soluble inositol (Ins) kinase activities (red arrows) of IPMK previously characterized in both in vitro and in vivo assays (for review see ref. 3). Also depicted is the lipid inositol PI3K activity being described. Additional activities not shown include the phosphorylation of Ins(4,5)P₂ to Ins(1,4,5)P₃ and the phosphorylation of Ins(1,4,5)P₃ first to Ins(1,4,5,6)P₄ and subsequently to Ins(1,3,4,5,6)P₅. More recently, human IPMK was shown to be capable of phosphorylating Ins(1,3,4,6)P₄ to Ins(1,3,4,5,6)P₅ (19).