BIOL 4087 Chapter : Chapter 18 Nucleotide Metabolism
Document Summary
Recycling of bases to nucleotide is active and saves energy for anabolic processes salvage. Complete catabolism of all purine bases are carried out after transforming all into hypoxanthine. In humans and higher primates, uric acid is the final oxidation (breakdown) product of purin metabolism and is excreted in urine. In most other mammals, the enzyme uricase further oxidizes uric acid to allantoin. The loss of uricase in higher primates parallels the similar loss of the ability to synthesize ascorbic acid, leading to the suggestion that urate may partially substitute for ascorbate in such species. Both uric acid and ascorbic acid are strong reducing agents (electron donors) and potent antioxidants. In humans, over half the antioxidant capacity of blood plasma comes from uric acid. Diseases in nucleic acid metabolism: gout ---- inadequate secretion of uric acid. Pyrimidine: base is separately made and then linked to rib-5-p. Purine nucleotide: imp is made first using glu, gly, co2, and asp.
