Besides the ribonucleoside monophosphates, ribonucleoside diphosphates and ribonucleoside triphosphates are important metabolites.
There are also deoxynucleoside mono-, di and triphosphates.
The phosphates are usually esterified to the 5'-hydroxyl group.
Several enzymes catalyze the phosphorylation of nucleoside monophosphates, and a single enzyme (nucleoside diphosphate kinase) catalyzes the phosphorylation of all the diphosphates (see Chapter 6)