In enzymology, a purine-nucleoside phosphorylase (EC 188.8.131.52) is an enzyme that catalyzes the chemical reaction:purine nucleoside + phosphate↔ purine + alpha-D-ribose 1-phosphate. Thus, the two substrates of this enzyme are purine nucleoside and phosphate, whereas its two products are purine and alpha-D-ribose 1-phosphate. This enzyme belongs to the family of glycosyltransferases, specifically the pentosyltransferases. This enzyme participates in 3 metabolic pathways:purine metabolism, pyrimidine metabolism, and nicotinate and nicotinamide metabolism.
PNP, Native (Microorganisms)
PNP; PNPase; PUNPI; PUNPII
Nucleoside phosphorylase is used in coupled enzyme systems to measure protein dephosphorylation. This enzyme is useful for enzymatic determination of inorganic phosphorus, 5′-nucleotidase and adenosine deaminase when coupled with xanthine oxidase (XTO-212) and uricase (UAO-201, UAO-211). Purine nucleoside phosophorylase has shown the ability to perform both phosphorylosis and synthesis of purine deoxy-and ribonucleosides. It has also been found that membrane-ass ociated nucleoside phosphorylases may have a transmembranal orientation with their base and ribose-1-P binding sites on opposite sides of the membrane.
Lyophilized powder containing potassium gluconate, mannitol and EDTA
Enzyme Commission Number
> 10 units/mg protein
mol wt ~120 kDa
pH 6.0-9.0 (30°C, 16hr)
6.4 x 10-5M (Inosine), 3.2x10-4M (Pi)
One unit will cause the phosphorolysis of 1.0 μmole of inosine to hypoxanthine and ribose 1-phosphate per min at pH 7.4 at 25°C.
below 60°C (pH 7.7, 30min)
p-Chloromercuribenzoate, SDS, Hg++, Ag+
purine-nucleoside phosphorylase; inosine phosphorylase; PNP; PNPase; PUNPI; PUNPII; inosine-guanosine phosphorylase; nucleotide phosphatase; purine deoxynucleoside phosphorylase; purine deoxyribonucleoside phosphorylase; purine nucleoside phosphorylase; purine ribonucleoside phosphorylase; 9030-21-1; EC 184.108.40.206