Lecture 14 - Purine Synthesis (salvage pathway) Flashcards
How much free purine is produced from purine degradation per day?
5g, but only 0.5g is excreted as uric acid
What happens to the remaining free purine that isn’t excreted?
Is recycled back to IMP, AMP, and GMP using the salvage pathway
How much ATP is needed to make AMP?
8
How much ATP is needed to make GMP?
9
What is Lesh-Nyhon syndrome?
A complete absence in the hypoxanthine-guanine-phosphoribosyl transferase enzyme
Describe the basis of the salvage pathway
AMP -> adenosine -> inosine -> hypoxanthine -> xanthine -> uric acid
What enzyme converts adenosine to AMP?
Adenine phosphoribosyl transferase
What are the 2 pathways to convert inosine to hypoxanthine?
- Directly, releasing ribose
- Inosine -> GMP -> guanosine -> guanine -> hypoxanthine
What is the enzyme and cofactor to convert guanine to GMP?
- Hypoxanthine-guanine phosphoribosyl transferase
- PRPP -> PPi
What is the enzyme and cofactor to convert hypoxanthine to inosine?
- Hypoxanthine-guanine phosphoribosyl transferase
- PRPP -> PPi
What is the enzyme and cofactor to convert hypoxanthine to xanthine?
- Xanthine oxidase
- H2O + O2 -> H2O2
What is the enzyme and cofactor to convert xanthine to uric acid?
- Xanthine oxidase
- H2O + O2 -> H2O2
What can IMP be converted to?
AMP and GMP
What is the predominant enzyme of the salvage pathway?
Hypoxanthine phosphoribosyl transferase
What is gout?
A partial PRTase deficiency, resulting in a buildup of PPRP and an overproduction of uric acid and sodium urate
