Purine nucleoside phosphorylase (PNP)
Cofactors used
Clinical / pharmacological. PNP deficiency: T-cell immunodeficiency
What it does, reaction by reaction
Purine Degradation (to Uric Acid) Nucleotide Metabolism · Cytosol
Inosine → hypoxanthine
Converts Inosine into Hypoxanthine
› Notes
PNP catalyzes inosine + Pi ⇌ hypoxanthine + ribose 1-phosphate. In catabolic tissues, the reaction commonly proceeds toward free hypoxanthine.
Guanosine → guanine
Converts Guanosine into Guanine
› Notes
PNP catalyzes guanosine + Pi ⇌ guanine + ribose 1-phosphate.
Purine Salvage Pathway Nucleotide Metabolism · Cytosol
Inosine → hypoxanthine + ribose 1-phosphate
Converts Inosine into Hypoxanthine Ribose-1-phosphate
› Notes
Purine nucleoside phosphorylase (PNP) catalyzes inosine + Pi ⇌ hypoxanthine + ribose 1-phosphate. Although this reaction is reversible and is often viewed as degradative, the liberated hypoxanthine can immediately enter the HGPRT reaction in an operational salvage sequence.
Guanosine → guanine + ribose 1-phosphate
Converts Guanosine into Guanine Ribose-1-phosphate
› Notes
PNP catalyzes guanosine + Pi ⇌ guanine + ribose 1-phosphate. Guanine can then be salvaged by HGPRT; direction in vivo depends on substrate and phosphate concentrations.
Showing all 4 reactions.
What accelerates and inhibits it
Regulation is pathway-specific, so each context is listed separately
No regulation recorded for this enzyme in the source documents.
Recent literature
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