What is the end product of purine catabolism in humans?

What is the end product of purine catabolism in humans?

• A. Urea
• B. Uric acid
• C. Allantoin
• D. Ammonia

Answer: (B)

Purine breakdown ends with uric acid in humans. Nucleotides are degraded through a series of steps that convert the purine ring ultimately to xanthine, and then to uric acid by the action of xanthine oxidase. Humans lack the enzyme uricase, so uric acid isn’t further oxidized to allantoin and is excreted as the final purine catabolite. This differs from urea, which comes from amino acid nitrogen via the urea cycle, and from allantoin, which is produced in species that possess uricase. Ammonia is an earlier, more general nitrogen waste product from deamination, not the terminal product of purine catabolism in humans.

Purine breakdown ends with uric acid in humans. Nucleotides are degraded through a series of steps that convert the purine ring ultimately to xanthine, and then to uric acid by the action of xanthine oxidase. Humans lack the enzyme uricase, so uric acid isn’t further oxidized to allantoin and is excreted as the final purine catabolite. This differs from urea, which comes from amino acid nitrogen via the urea cycle, and from allantoin, which is produced in species that possess uricase. Ammonia is an earlier, more general nitrogen waste product from deamination, not the terminal product of purine catabolism in humans.