 Type II PIPKs phosphorylate PtdIns5"P" at the D-4 site and are called PtdIns5"P" 4-kinases.And finally PIPKs of type III are PtdIns3"P" 5-kinases that phosphorylate PtdIns to PtdIns(3,5)"P"2, which prototype is Fab1 in yeast (see for descriptive picture).The substrate specificity of type I and II depends on the so-called activation loop.