Purine-nucleoside phosphorylase

In enzymology, a purine-nucleoside phosphorylase (EC 2.4.2.1) 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. The systematic name of this enzyme class is purine-nucleoside:phosphate ribosyltransferase. Other names in common use include inosine phosphorylase, PNPase, PUNPI, PUNPII, inosine-guanosine phosphorylase, nucleotide phosphatase, purine deoxynucleoside phosphorylase, purine deoxyribonucleoside phosphorylase, purine nucleoside phosphorylase, and purine ribonucleoside phosphorylase. This enzyme participates in 3 metabolic pathways: purine metabolism, pyrimidine metabolism, and nicotinate and nicotinamide metabolism.

Structural studies

As of late 2007, 85 structures have been solved for this class of enzymes, with PDB accession codes 1A69, 1A9O, 1A9P, 1A9Q, 1A9R, 1A9S, 1A9T, 1B8N, 1B8O, 1ECP, 1FXU, 1G2O, 1I80, 1K9S, 1LV8, 1LVU, 1M73, 1N3I, 1NW4, 1OTX, 1OTY, 1OU4, 1OUM, 1OV6, 1OVG, 1PBN, 1PF7, 1PK7, 1PK9, 1PKE, 1PR0, 1PR1, 1PR2, 1PR4, 1PR5, 1PR6, 1PW7, 1PWY, 1Q1G, 1QE5, 1RCT, 1RFG, 1RR6, 1RSZ, 1RT9, 1TCU, 1TCV, 1TD1, 1ULA, 1ULB, 1V2H, 1V3Q, 1V41, 1V45, 1V48, 1VFN, 1VHJ, 1VHW, 1VMK, 1XE3, 1YQQ, 1YRY, 1Z33, 1Z34, 1Z35, 1Z36, 1Z37, 1Z38, 1Z39, 2A0W, 2A0X, 2A0Y, 2AC7, 2AI1, 2AI2, 2AI3, 2B94, 2BSX, 2I4T, 2ISC, 2OC4, 2OC9, 2ON6, 3PNP, and 4PNP.

References

• Agarwal RP, Parks RE Jr (1969). "Purine nucleoside phosphorylase from human erythrocytes. IV Crystallization and some properties". J. Biol. Chem. 244 (4): 644–7. PMID 5768862. 
• Boyer, P.D., Lardy, H. and Myrback, K. (Eds.), The Enzymes, 2nd ed., vol. 5, Academic Press, New York, 1961, p. 237-255.
• HEPPEL LA, HILMOE RJ (1952). "[Phosphorolysis and hydrolysis of purine ribosides by enzymes from yeast.]". J. Biol. Chem. 198 (2): 683–94. PMID 12999785. 
• Kalckar HM (1947). "The enzymatic synthesis of purine ribosides". J. Biol. Chem. 167: 477–486. PMID 20285042. 
• Saunders PP, Wilson BA, Saunders GF (1969). "Purification and comparative properties of a pyrimidine nucleoside phosphorylase from Bacillus stearothermophilus". J. Biol. Chem. 244 (13): 3691–7. PMID 4978445. 
• Tsuboi KK and Hudson PB (1957). "Enzymes of the human erythrocyte. I. Purine nucleoside phosphorylase; isolation procedure". J. Biol. Chem. 224: 879–887. PMID 13405917.