Nucleoside Phosphorylase from microorganisms

Nucleoside Phosphorylase are trimeric and have a molecular mass of about 100 kDa. Each monomer consists of a mixed β-sheet core flanked by eight α-helices and a purine binding in hydrophobic pocket.

Nucleoside phosphorylase is an enzyme important for the biosynthesis of nucleosides.

Isoelectric point : 4.1 +/- 0.1
Michaelis constants : 6.4 x 10^-5M (Inosine), 3.2x10^-4M (Pi)
Inhibitors : p-Chloromercuribenzoate, SDS, Hg⁺⁺, Ag⁺Optimum pH : 7.5 - 8.0
Optimum temperature : 65o^C
pH Stability : pH 6.0 - 9.0 (30o^C, 16hr)
Thermal stability : below 60o^C (pH 7.7, 30min)

Nucleoside Phosphorylase from microorganisms has been used:

• in phosphopentomutase assay for adenosine synthesis
• for the conversion of 7-methylthioguanosine to 7-methylthioguanine
• in the synthesis of cytokinins in lyophilized cotton plant samples

Nucleoside phosphorylase is used in coupled enzyme systems to measure protein dephosphorylation.

Nucleoside Phosphorylase catalyzes the synthesis of nucleoside derivatives.

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-associated nucleoside phosphorylases may have a transmembranal orientation with their base and ribose-1-P binding sites on opposite sides of the membrane.

Catalyzes the following reaction:purine nucleoside + phosphate = purine + alpha-D-ribose 1-phosphate

Lyophilized powder containing potassium gluconate, mannitol and EDTA

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.