Hypoxanthine Guanine Phosphoribosyl Transferase is associated with the conversion of uric acid to which compound?

• A. Purine
• B. Uric Acid
• C. Xanthine
• D. Hypoxanthine

Answer: (A)

Purine salvage is the process being tested. HGPRT catalyzes the attachment of ribose-5-phosphate from PRPP to free purine bases, specifically hypoxanthine and guanine, to form the nucleotide monophosphates IMP and GMP. This salvages purines and keeps them from being degraded to uric acid, effectively linking HGPRT activity to production of purine nucleotides rather than allowing further breakdown. Therefore, the product associated with this enzyme’s action is a purine nucleotide.

Uric acid is the end product of purine catabolism, not a product of salvage. Xanthine is an intermediate in the degradation pathway, not the product of HGPRT’s salvage reaction. Hypoxanthine is a substrate for HGPRT, not the product.