21.Degradation Of Purine Nucleotides
Quick Notes •
Because nucleic acids are ubiquitous in cellular material, significant amounts are ingested in the diet. Nucleic acids are degraded in the digestive tract to nucleotides by various nucleases and phosphodiesterases. • Nucleotides are then converted to nucleosides by base-specific nucleotidases and nonspecific phosphatases. NMP + H2O --->nucleoside + Pi • The various nucleotides are first converted to nucleosides by intracellular nucleotidases. Nucleosides are then degraded by the enzyme purine nucleoside phosphorylase (PNP) to release the purine base and ribose-l-P. The PNP products are merged into xanthine by guanine deaminase and xanthine oxidase, and xanthine is then oxidized to uric acid by this latter enzyme.