Purine Metabolism - Exam 1 Flashcards
Nucleotides serve all of the following roles EXCEPT
Structural components of membranes
ribose with nucleotides
purines built on pyrimidines built then on
whites not a purine
cytosine
which of the following does not serve as a source of C in purine ring synthesis?
aspartate
glutamine
sources of nitrogen
2 glu
1 asp
1 gly
sources of carbon
2 gly
1 CO2
2 N10-fTHF
synthesis of PRPP
from ribose 5-phosphate
activated by Pi
inhibited by purines
R 5-p is produced from glucose by
PPP (also produces NADPH…)
first committed step
PRPP to 5-phosphoribosyl 1-amine
rate limiting steps
prpp synthetase: feedback inhibition Glutamine PRPP amidotransferase: AMP GMP inhibits Stimulated by PRPP (feed forward)
PABA analogs
slow down purine synthesis in bacteria
methotrexate
slows down purine synthesis in humans
methotrexate affects nucleotide synthesis by limiting THF by inhibiting
dihydrofolate reductase
first purine nucleotide
IMP (base or ring is hypoxanthine)
needed for AMP synthesis
GTP
needed for GMP synthesis
ATP
mycophenolic acid
immunosupressent for graft rejection
electron source for ribonucleotide reductase (RNR)
NADPH
most purine synthesis occurs in
liver
most ingested are degraded and excreted
PNP deficiency
IMMUNODEFICIENCY
ADA deficiency
SCID
PRTs
HG and A h=hypoxanthine
defective HGPRTase
Lesch-Nyhan gouty self-mutilation retardation lip and finger biting!!
uric acid is
formed from xanthine in the presence of O2
Hyperuricemia
progresses to gout
lactic acidosis, lead both interfere with excretion
PRPP working overtime…
gout - DX
negative birefringent urate crystals in the synovial fluid
kidney stones
can be same
gout - TX
allopurinol
low purine diet
Lesch-Nyhan is due to the inability to catalyze which reaction
guanine to GMP
SCID
ADA def
B, T, and NK cells can’t divide
must diagnose early
