Flashcards in Purine, Pyrimidine, and Nucleotide Metabolism - Parts 1 & 2 Deck (27):
___________ have two rings.
Compare and contrast the starting points for the synthesis of purines and pyrimidines.
Purines: starts with ribose
Pyrimidines: starts with base and adds sugar at the end
The form of __________ in the mitochondria takes part in the urea cycle, while the cytosolic form participates in pyrimidine synthesis.
carbamoyl phosphate synthase
In purine synthesis, ___________ is converted to AMP and GMP.
__________ is converted to CTP.
What is the first step in purine synthesis?
(PRPP synthetase) ***Regulated step***
After PRPP synthetase, what is the next regulated step in the synthesis of IMP?
(Glutamine phosphoribosyl pyrophosphate amidotransferase) ***Inhibited by GMP, AMP, and IMP; activated by PRPP***
These two enzymes are both allosterically inhibited by IMP, GMP, and AMP: _______________.
PRPP synthetase and glutamine PRPP amidotransferase
The key regulated enzyme in pyrimidine synthesis is _________________.
2x ATP + CO2 + glutamate
(Carbamoyl phosphate synthetase II [in the cytosol])
Ribonucleosides are converted to deoxyribonucleosides by the enzyme _________________.
ATP _____________ ribonucleotide reductase, while dATP _____________ it.
Allopurinol inhibits ______________.
What enzyme converts adenosine to inosine?
The two key enzymes in purine degradation are ________________.
(1) adenosine deaminase and (2) xanthine oxidase
Those with Lesch-Nyhan cannot convert ________ to __________ or __________ to __________.
Nucleoside is ______________, while nucleotide is _______________.
base and sugar; base, sugar, and phosphate
In general, the body relies on ______________ when it needs nucleotides.
the salvage pathway
True or false: methotrexate inhibits the production of pyrimidines.
What is created first in the pyrimidine synthesis pathway?
UMP; it must be converted to UTP before being converted to CTP
The enzyme ribonucleotide reductase is inhibited by ____________.
Ribonucleotide reductase does not recognize _______.
TMP, so to get dTMP you need to make dUDP first
Describe the overall process of purine breakdown.
First, the base is separated from the sugar, then the base is broken down to uric acid and excreted in the urine.
After pyrimidines are separated from their sugars, what happens?
The ring is broken open.
PRPP synthase is activated by high amounts of ______________.
5-flurouracil inhibits the synthesis of _____________.
dTMP (because 5FU enters the enzyme thymidylate synthase and inhibits it)
Without adenosine deaminase, dATP builds up in the blood. Why is this a problem?
Because dATP is a potent inhibitor of DNA synthesis