XMP is an intermediate in the de novo biosynthesis of GMP (Figure 22.6). It is acted on by the enzyme IMP dehydrogenase, as follows:

Inosine Monophosphate (IMP) +  NAD⁺ + H2O <=> Xanthosine Monophosphate (XMP) + NADH + H⁺ 

Subsequently, XMP is converted to GMP by the enzyme XMP aminase (Figure 22.6).