Biochemistry Flashcards
Is hyperuricemia both necessary and sufficient for the diagnosis of gout? Explain
It is necessary though alone is insufficient to explain gout, as many Americans have hyperuricemia but not gout.
What’s unique about uric acids structure?
It’s the most oxidized purine having 3 ketones. This is because it is the end product of nucleotide degradation and can only be excreted by urine or feces.
Do not mistake it for uracil (pyrimidine), or urea.
What enzyme converts ATP to AMP and how does it work?
PRPP synthetase. The anameric carbon of ribose-5-phosphate attacks the beta phosphate of ATP to make PRPP and AMP.
What type of reaction converts a nucleotide to a nucleoside?
oxidation reaction. This reaction dominates: purine degradation, drug degradation, and glucose degradation
Nucleotide has base, sugar, and phosphate
NucleoSide has just base and Sugar.
What’s so special about inosine and how is it formed?
It is involved in making and breaking purine nucleotides
and is an oxidized (lower energy form) of Adenine
What do the enzymes AMP deaminase and Adenosine deaminase do?
AMP deaminase removes an amine group from AMP
and Adenosine deaminase removes an amine group from the Adenine nucleoside
When Inosine is oxidized what is the eventual end product of this oxidation and which enzymes are involved?
Inosine–> Hypoxanthine–(xanthine oxidase)–> xanthine–(xanthine oxidase)–> uric acid.
Explain how purine synthesis is inhibited by AMP and GMP
They work as a negative feedback mechanism on themselves as they accumulate.
If the de-novo biosynthesis of purines is high in the liver and these are catabolized rapidly, what condition can result?
hyperuricemia from purines being oxidized to form uric acid.
Name at least 4 ways in which you can increase uric acid in the body. Give examples of each
Dietary purine intake and oxidation
red meat, seafood, beer
De novo biosynthesis in the liver
Fructose, lesch Nyhan syndrome
Reabsorption in the kidney
ETOH, fructose
Inadequate filtration in the kidney
damage
