Title: OVERVIEW OF AMINO ACID METABOLISM
1OVERVIEW OF AMINO ACID METABOLISM
ENVIRONMENT
ORGANISM
Bio- synthesis
Protein
Ingested protein
2
3
1
a
AMINO ACIDS
b
Degradation (required)
c
c
Purines Pyrimidines Porphyrins
Nitrogen
Carbon skeletons
Urea
pyruvate a-ketoglutarate succinyl-CoA fumarate o
xaloacetate
(glucogenic)
(ketogenic)
Used for energy
acetoacetate acetyl CoA
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3NITROGEN BALANCE
Nitrogen balance nitrogen ingested -
nitrogen excreted
(primarily as protein) (primarily as urea)
Nitrogen balance 0 (nitrogen equilibrium)
protein synthesis
protein degradation
Positive nitrogen balance
protein synthesis gt protein
degradation
Negative nitrogen balance
protein synthesis lt protein
degradation
4TRANSAMINATION
5UREA CYCLE
mitochondria
cytosol
Function detoxification of ammonia (prevents
hyperammonemia)
6FATE OF THE CARBON SKELETONS
Carbon skeletons are used for energy.
Glucogenic TCA cycle intermediates
or pyruvate (gluconeogensis)
Ketogenic acetyl CoA, acetoacetyl CoA,
or acetoacetate
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8Purine and Pyrimidine Metabolism
9Major Bases
10Source of each atom in the purine ring
11 Summary and Regulation
12Inhibition of Purine Biosynthesis by the
Antitumor Agent, 6-Mercaptopurine
- 6-Mercaptopurine is converted to a nucleotide.
- The nucleotide inhibits purine biosynthesis at
steps 2, 12a, 12b, and 13a.
13Major Bases
14Sources of the atoms of the pyrimidine ring
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16DNA and RNA Degradation
17Salvage Pathway for Purines (90)
Lesch-Nyhan Syndrome
18Degradation of Purines (10)
19Allopurinol Inhibits xanthine oxidase
X
X
20Heme
21 Structure
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23Porphyrias
24hemoglobin
globin
heme
Fe (reutilized)
degraded (bilirubin)
free amino acids
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26HYPERBILIRUBINEMIA
-- elevated bilirubin in serum (above 1 mg/dL)
-- can be conjugated or unconjugated or both
depending on the situation
-- elevated bilirubin can diffuse into tissues,
making them appear yellow (jaundice)
27HYPERBILIRUBINEMIA Clinical Consequences
-- Conjugated hyperbilirubinemia benign
-- Unconjugated hyperbilirubinemia benign at
concentrations lt 25 mg/dL (albumin capacity)
-- At concentrations gt25 mg/dL, unconjugated
bilirubin is free (uncomplexed) and can enter
the brain.
28Causes of JAUNDICE
- Hemolytic anemia
- -- ? destruction of erythrocytes
- Hepatitis or cirrhosis
- -- ? conjugation and excretion of bilirubin
- Bile duct obstruction
- -- conjugated bilirubin not delivered to
intestine - it backs up, spills over into the
blood
- Neonatal physiological jaundice
- -- immature hepatic system of the newborn
- ? uptake, conjugation, excretion of
bilirubin