Figure 2: Catalytic reactions of IPCT/DIPPS bifunctional enzyme.

Biosynthesis of di-myo-inositol-1,3′-phosphate-1′-phosphate (DIPP). IPCT-CTP:L-myo-inositol-1-phosphate cytidylyltransferase; DIPPS-CDP-L-myo-inositol:myo-inositolphosphotransferase or DIPP synthase; PPi-pyrophosphate; CMP, CDP, CTP- cytidine mono-, di-, tri- phosphate, respectively. The dashed red line represents the nucleophilic attack of the hydroxyl group (C3) of inositol-1-phosphate on the β-phosphoryl of CDP-inositol with formation of a phosphodiester bond.