Ins(1,4,5,6)P4, a biol. active cell constituent, was recently advocated as a substrate of human Ins(3,4,5,6)P4 1-kinase (hITPK1), because stereochemistry factors were believed relatively unimportant to specificity. Ins(1,4,5,6)P4 is phosphorylated by inositol-phosphate-multikinase but not human ITPK1.