Xanthosine Monophosphate (XMP)

Xanthosine monophosphate is an intermediate in purine metabolism. It is a ribonucleoside monophosphate. It is formed from IMP via the action of IMP dehydrogenase, and it forms GMP via the action of GMP synthase. Also, XMP can be released from XTP by enzyme deoxyribonucleoside triphosphate pyrophosphohydrolase containing (d)XTPase activity. Xanthosine is a nucleoside derived from xanthine and ribose. It is the biosynthetic precursor to 7-methylxanthosine by the action of 7-methylxanthosine synthase.  The four acidity constants of threefold protonated xanthosine 5"""-monophosphate, H3(XMP)+, reveal that at the physiological pH of 7.5 (XMP-H)(3-) strongly dominates (and not XMP(2-) as given in textbooks); this is in contrast to the related inosine (IMP(2-)) and guanosine 5"""-monophosphate (GMP(2-)) and it means that XMP should better be named as xanthosinate 5"""-monophosphate.