Nucleoside phosphorylase

Both purine and pyrimidine phosphorylase enzymes are done viz. the nucleotide salvage pathway. The salvage pathway is a method for the cell to produce nucleotide monophosphates when the de novo synthesis pathway has been interrupted. The de novo pathway is normally interrupted by the way of chemotherapy drugs such as methotrexate or aminopterin.

All salvage pathway enzymes require a high energy phosphate donor such as ATP or PRPP.


 * Thymidine can be phosphorylated by thymidine kinase (TK).
 * Uridine can be phosphorylated by uridine kinase (UK).
 * Cytidine can be phosphorylated by cytidine kinase (CK).
 * Deoxycytidine can be phosphorylated by deoxycytidine kinase (DOK).

Adenosine uses the enzyme adenosine kinase, which is a very important enzyme in the cell. Many attempts are being made to develop an inhibitor for the enzyme in cancer chemotherapy.