Purine Synthesis and Degradation Flashcards
what is on a nucleoside?
base and sugar
what is on a nucleotide?
base sugar and phosphate group
common name endings for nucleosides
- dine
- sine
What do you need to start purine synthesis?
ribose-5-phosphate and ATP
Where do we get ribose-5-phosphate from to start the purine synthesis?
from the pentose phosphate pathway
What is the first step of purine synthesis?
turning ribose-5-phosphate into 5-phosphoribosyl-1-pyrophosphate (PRPP)
What is the enzyme that turns ribose-5-phosphate into PRPP?
PRPP synthetase
What inhibits PRPP synthetase?
nucleotides…if you have a lot you do not need to be making more
PRPP sythetase disorder name
Arts syndrome….low numbers of nucleotides
What is the committed step of purine synthesis?
adding an amine to the PRPP molecule to make 5-phosphoribosyl 1-amine
What is the enzyme that turns PRPP into 5-phosphoribosyl-1amine?
glutamine phosphoribosyl amidotransferase
What molecules help build the purine ring?
amino acids, CO2 and THF
What molecule activates and what molecule inhibits the glutamine phosphoribosyl amidotransferase?
PRPP activates and nucleotides inhibit
What is the precursor for AMP and GMP?
IMP
How do we make sure we make even amounts of AMP and GMP?
AMP and GMP crossregulate each others enzymes that use IMP
What enzyme does mycophenolate attack to inhibit GMP synthesis?
IMP dehydrogenase
What enzyme turns AMP into ADP?
Adenylate kinase
What enzyme turns GMP into GDP?
Guanylate kinase
What enzyme turns ADP and GDP into ATP and GTP?
nucleoside diphosphate kinase
What does degradation of purines lead to?
Xanthine and then uric acid
What happens if you have too much purine degradation leading to hyperuricemia?
GOUT
allopurinol
drug for treatment of hyperuricemia
Adenosine initially gets broken down into what molecule?
Inosine
What are the two enzymes that can make adenosine into inosine?
AMP deaminase and adeonsine deaminase
What happens if you have adenosine deaminase deficiency?
leads to accumulation of the adenosine and deoxyadenosine molecules…deoxyadenosine is toxic
SCID
What enzyme makes IMP into AMP?
adenylosuccinate synthetase
What enzymes makes IMP into GMP?
IMP dehydrogenase
