Pyrimidine Nncleosides

To convert pnrine and pyrimidine nncleoside monophosphates to triphosphates, two kinase enzymes are required mono- and di-nncleotide kinases. For example. 

The term nucleoside was once restricted to pyrimidine and purine A-glycosides of D-ribofnranose and 2-deoxy-D-ribofuranose, becanse these are the substances present in nncleic acids. The term is nsed more liberally now with respect to the carbohydrate portion, bnt is still nsnally limited to pyrimidine and pnrine snbstitnents at the anomeric carbon. Uridine is a representative pyrimidine nncleoside it bears a D-ribofuranose gronp at N-1. Adenosine is a representative purine nncleoside its carbohydrate unit is attached at N-9. 

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