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Figure 28-1
The biosynthetic origins of purine ring atoms.
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Figure 28-2 The metabolic pathway for the de novo
biosynthesis of IMP.
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Figure 28-3 The proposed mechanism of
formylglycinamide ribotide (FGAM) synthetase.
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Figure 28-4 IMP is converted to AMP or GMP in separate
two-reaction pathways.
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Figure 28-5
pathway.
Control network for the purine biosynthesis
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Figure 28-6
atoms.
The biosynthetic origins of pyrimidine ring
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Figure 28-7
of UMP.
Metabolic pathway for the de novo synthesis
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Figure 28-8 Reactions catalyzed by eukaryotic
dihydroorotate dehydrogenase.
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Figure 28-9 Proposed catalytic mechanism for OMP
decarboxylase.
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Figure 28-10 Synthesis of CTP from UTP.
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Figure 28-11 Regulation of pyrimidine biosynthesis. The
control networks are shown for (a) E. coli and (b) animals.
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Figure 28-12a Class I ribonucleotide reductase from E.
coli. (a) A schematic diagram of its quaternary structure.
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Figure 28-12b Class I ribonucleotide reductase from E.
coli. (b) The X-ray structure of R22.
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Figure 28-12c Class I ribonucleotide reductase from E.
coli. (c) The binuclear Fe(III) complex of R2.
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Figure 28-12d Class I ribonucleotide reductase from E.
coli. (d) The X-ray structure of the R1 dimer.
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Figure 28-13 Enzymatic mechanism of ribonucleotide
reductase.
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Figure 28-14a Ribonucleotide reductase regulation. (a) A
model for the allosteric regulation of Class I RNR via its
oligomerization.
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Figure 28-14b Ribonucleotide reductase regulation. (b) The
X-ray structure of the R1 hexamer, which has D3 symmetry,
in complex with ADPNP as viewed along its 3-fold axis.
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Figure 28-14c Ribonucleotide reductase regulation. (c) The
R1·ADPNP hexamer as viewed along the vertical 2-fold axis
in Part b.
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Figure 28-15 X-Ray structure of human thioredoxin in its
reduced (sulfhydryl) state.
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Figure 28-16 Electron-transfer pathway for nucleoside
diphosphate (NDP) reduction.
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Figure 28-17a X-Ray structures of E. coli thioredoxin
reductase (TrxR). (a) The C138S mutant TrxR in complex
with NADP+.
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Figure 28-17b The C135S mutant thioredoxin reductase
(TrxR) in complex with AADP+, disulfide-linked to the C35S
mutant of Trx.
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Figure 28-18a X-Ray structure of human dUTPase. (a) The
molecular surface at the substrate binding site showing how
the enzyme differentiates uracil from thymine.
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Figure 28-18b X-Ray structure of human dUTPase. (b) The
substrate binding site indicating how the enzyme differentiates
uracil from cytosine and 2-deoxyribose from ribose.
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Figure 28-19 Catalytic mechanism of thymidylate synthase.
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Figure 28-20 The X-ray structure of the E. coli thymidylate
synthase–FdUMP–THF ternary complex.
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Figure 28-21 Regeneration of N5,N10methylenetetrahydrofolate.
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Figure 28-22 Ribbon diagram of human dihydrofolate
reductase in complex with folate.
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Figure 28-23 Major pathways of purine catabolism in
animals.
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Figure 28-24a Structure and mechanism of adenosine
deaminase. (a) A ribbon diagram of murine adenosine
deaminase in complex with its transition state analog HDPR.
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Figure 28-24b Structure and mechanism of adenosine
deaminase. (b) The proposed catalytic mechanism of
adenosine deaminase.
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Figure 28-25 The purine nucleotide cycle.
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Figure 28-26a X-Ray structure of xanthine oxidase from
cow’s milk in complex with salicylic acid. (a) Ribbon diagram
of its 1332-residue subunit.
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Figure 28-26b X-Ray structure of xanthine oxidase from
cow’s milk in complex with salicylic acid. (b) The enzyme’s
redox cofactors and salicylic acid (Sal).
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Figure 28-27 Mechanism of xanthine oxidase.
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Figure 28-28 Degradation of uric acid to ammonia.
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Figure 28-29 The Gout, a cartoon by James Gilroy (1799).
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Figure 28-30 Major pathways of pyrimidine catabolism in
animals.
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Figure 28-31 Pathways for the biosynthesis of NAD+ and
NADP+.
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Figure 28-32 Biosynthesis of FMN and FAD from the
vitamin precursor riboflavin.
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Figure 28-33 Biosynthesis of coenzyme A from
pantothenate, its vitamin precursor.