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15 Cards in this Set

  • Front
  • Back
Lesch-Nyhan Syndrome
-Absence of HPGRTase
-X-linked (occurs primarily in males)
Characterized By:
-increased uric acid
-neurological defects
-aggresive behavior
-self mutilation

-nerve cells rely on salvage pathway
-many pro-drugs need to go through the salvage pathway to be activated
-Ex. 6-Mercaptopurine & 6-Thioguanine --> antitumor agents
6-Mercaptopurine & 6-Thioguanine
-antitumor agents
-act as inhibitors of adenylsuccinate synthase & IMP dehydrogenase
-also act as feedback inhibitors of PRPP amidotransferase
Purine Nusleoside Phosphorylase Deficiency
-PNP deficiency causes
decreased T cells and
lymphopenia, but does not
appear to effect B-cells
-Decrease in uric acid
formation, combined with
increased levels of purine
nucleosides and nucleotides.
-dGTP is the major nucleotide
that accumulates in red cells.
-Treatment: bone-marrow
Adenosine Deaminase Deficiency
-Causes severe combined
immunodeficiency (SCID)
involving T-cell and usually
B-cell dysfunction.
-Extremely large buildups of
dATP in red cells have been
observed. (dATP is an
inhibitor of ribonucleotide
reductase, and therefore, of
DNA synthesis)
-ADA-deficient children
usually die before 2 years of
age from overwhelming
-Treatment: bone-marrow

-wipes out entire immune system --> think bubble boy
-Characterized by
hyperuricemia, with recurrent
attacks of acute arthritic joint
inflammation caused by
deposition of Sodium Urate
-Primary gout (hyperuricemia)
is the form of the disease
that is attributable to an
inborn error metabolism (i.e.
over production of uric acid)
-Secondary hyperuricemia
may be caused by other
diseases (e.g. cancer,
chronic renal insufficinecy,
HGPRT deficiency, etc.)
-Treatment: allopurinol
inhibits xanthine oxidase,
which results in an
accumulation of more
soluble hypoxanthine and
Main Differences Between Purine & Pyrimidine Synthesis
-Pyrimidine rings are assembled as a free base before attached to the ribose ring. The purine ring is assembled on the ribose.
-Purine synthesis follows a branched pathway --> AMP & GMP are synthesized from IMP
-Pyrimidine Synthesis follows an unbranched pathway --> CTP is synthesized from UTP
Carbamoyl Phosphate Synthetase II
-The enzyme CPS II shows a long solvent-protected channel running through the center of the enzyme.
-This allows the highly reactive intermediate to travel from one active site to the other.
-CPS II channel helps isolate from water
CPS II Inhibition/Activation
-inhibition (allosterically regulated) by UTP, a product of the pathway
-activated (allosterically regulated) by ATP & PRPP
Aspartate Transcarbamylase Reugulation
-allosterically regulated by CTP in some microorganisms (but not eukaryotes)
-a 2 electron acceptor (H+)
-mostly used as a cofactor for catabolic enzymes
beta-aminoisobutyrate found in blood
-is a sign of DNA degradation/turnover
Pyrimidine Salvage
-Can also be salvaged by reactions with PRPP
-Catalyzed by Pyrimidine phosphoribosyltransferase (PPRTase)
-Degredation pathways are quite distinct for purines and pyrimidines, but salvage pathways are quite similar
Synthesis of deoxyribonucleotides
-coversion of ribonucleotides to deoxyribonucleotides
-catalyzed by ribonucleotide reductase
Ribonucleotide Reductase
-2 R1 subunits (small subunits)
-2 R2 subunits (large subunits)
-catalyzes the reduction of ribinucleotides to deoxyribonucleotides