These metabolic reactions account for the synthesis of diphosphoinositol polyphosphates in both yeasts and mammalian cells. In the abbreviations of the chemical structures, “Ins” indicates the myo-inositol skeleton. The number of monophosphates around the inositol ring is denoted as a suffix after the ‘P’. The prefixes denote the number of diphosphates (PP). The schematic shows reactions catalyzed by the IP5K (also known as IPK1; black arrow), the IP6Ks (green arrows), and the Vip1/PPIP5Ks (blue arrows). The position of the diphosphate at the 1-position is an arbitrary choice between the two available options, namely, the 1- and 3-positions (see text for details). So as to simplify the figure, the reactions catalyzed by the DIPP phosphatases are not shown.