Function
Purine nucleoside phosphorylase is an enzyme involved in purine metabolism. PNP metabolizes adenosine into adenine, inosine into hypoxanthine, and guanosine into guanine, in each case creating ribose phosphate.
Nucleoside phosphorylase is an enzyme which cleaves a nucleoside by phosphorylating the ribose to produce a nucleobase and ribose 1 phosphate. It is one enzyme of the nucleotide salvage pathways. These pathways allow the cell to produce nucleotide monophosphates when the de novo synthesis pathway has been interrupted or is non-existent (as is the case in the brain). Often the de novo pathway is interrupted as a result 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 (DCK).
Adenosine uses the enzyme adenosine kinase, which is a very important enzyme in the cell. Attempts are being made to develop an inhibitor for the enzyme for use in cancer chemotherapy.
Read more about this topic: Purine Nucleoside Phosphorylase
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