Flashcards in Nucleotide Metabolism (Purines) Deck (43)
What is the base found in Inosine Monophosphate (IMP), an intermediate in purine synthesis and degradation?
Which base is found in xanthosine MP, an intermediate in purine synthesis and degradation?
Unusual bases found mainly in tRNA, but also in viral DNA, are often _________ of the major bases.
Addition of a _________ to the base produces a nucleoside.
The phosphate groups in nucleotides are responsible for the ___________associated with RNA and DNA.
Purine nucleotide synthesis has two pathways. What are they?
In humans, all of the enzymes necessary for de novo purine synthesis are found in the __________of the cell.
Before purine synthesis can take place____________ , is produced from __________ and ________by _________.
ribose phosphate pyrophosphokinase
What reaction does PRPP synthetase catalyze?
Ribose - 5 - phosphate to 5-Phophoribosyl-1-pyrophosphate
The first step of de novo purine synthesis is the committed and rate-limiting step. This reaction converts PRPP ---> 5-phosphoribosylamine using which enzyme?
Glutamine:phosphoribosyl pyrophosphate amidotransferase
The rate of the reaction catalyzed by Glutamine:phosphoribosyl pyrophosphate amidotransferase is controlled by the intracellular concentrations of what?
Glutamine and PRPP
The rate of the reaction catalyzed by Glutamine:phosphoribosyl pyrophosphate amidotransferase is inhibited by what?
How would you describe megaloblastic anemia?
Folate deficiencies in which hemoglobin levels are low and the bone marrow shows abnormally high numbers of megaloblastic cells (large abnormal immature erythrocytes)
Cancer cells can become resistant to MTX by amplification of the gene for what enzyme?
Synthesis of AMP from IMP requires...
GTP (adenylosuccinate synthetase)
Synthesis of GMP from xanthosine monophosphate requires ...
The nucleotide monophosphates (NMP) are finally converted to NDP and NTP by __________and ____________, respectively.
nucleoside monophosphate kinases (base specific)
nucleoside diphosphate kinases
Mycophenolic acid is an inhibitor of what enzyme?
Inosine monoposphate dehydrogenase
(T/F) Purines that result from normal turn over of cellular nucleic acids or that are obtained from the diet and not degraded can be salvaged
Purine salvage involved which two enzymes?
Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
Adenine phosphoribosyltransferase (APRT)
Hypoxanthine is converted to IMP in thr purine salvage pathway by what enzyme?
Guanine is converted to GMP in the purine salvage pathway by which enzyme?
Which reactions use HGPRT?
Hypoxanthine --> IMP
Guanine --> GMP
Adenine to AMP in the purine salvage pathway is catalyzed by which enzyme?
What type of disorder is Lesch-Nyhan syndrome? Resulting from a deficiency of what enzyme?
Lesch-Nyhan Syndrome results in an inability to do what?
Salvage the purines:
What is the end product of degredation of hypoxanthine and guanine in Lesch-Nyhan?
_______ are often found in the diapers of infants with Lesch-Nyhan Syndrome
A patient who comes to you with severe mental retardation, self-mutilation, involuntary movements, and gout most likely has what syndrome?
Lesch-Nyhan Syndrome causes increased _______levels and an increase in ______
de novo purine synthesis
Most purines in the diet are degraded to _______ rather than salvaged.
While purines are degraded to ________, pyrimidines are ________ and returned to _______
-absorbed in the intestinal mucosa
Adenosine deaminase (ADA) deficiency causes a type of ____________, involving _______ and _______ depletion. (______________)
-Severe combined immunodeficiency (SCID)
Why does ADA deficiency produce lymphocytopenia?
DNA is not synthesized in T-cells and B-cells because of an accumulation of dATP
In ADA deficiency, _______ and ______ are better substrates for purine nucleoside phosphorylase than is adenosine.
In ADA deficiency, dATP accumulates and causes inhibition of which enzyme?
Purine nucleoside phosphorylase (PNP) deficiency causes impairment of the function of what?
Decreased uric acid production and increased purine nucleoside and nucleotide production is characteristic of what?
Lab tests of a patient in your care return showing hyperuricemia and acute arthritic joint inflammation caused by deposition of uric acid crystals. This patients most likely has which disorder?
What characterizes Primary Gout?
-Affects mainly males over 30
What characterized Secondary Gout?
Brought on by a number of disorders including:
-treatment of cancer with antimetabolites
-Chronic renal insufficiency
Gout can be diagnosed by the presence of negatively birefringent ____________ crystals in aspirated synovial fluid examined by polarized-light microscopy