OVERVIEW OF AMINO ACID METABOLISM - PowerPoint PPT Presentation

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OVERVIEW OF AMINO ACID METABOLISM

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Title: OVERVIEW OF AMINO ACID METABOLISM


1
OVERVIEW 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
2
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3
NITROGEN 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
4
TRANSAMINATION
5
UREA CYCLE
mitochondria
cytosol
Function detoxification of ammonia (prevents
hyperammonemia)
6
FATE OF THE CARBON SKELETONS
Carbon skeletons are used for energy.
Glucogenic TCA cycle intermediates
or pyruvate (gluconeogensis)
Ketogenic acetyl CoA, acetoacetyl CoA,
or acetoacetate
7
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8
Purine and Pyrimidine Metabolism
9
Major Bases
10
Source of each atom in the purine ring
11
Summary and Regulation
12
Inhibition of Purine Biosynthesis by the
Antitumor Agent, 6-Mercaptopurine
  1. 6-Mercaptopurine is converted to a nucleotide.
  2. The nucleotide inhibits purine biosynthesis at
    steps 2, 12a, 12b, and 13a.

13
Major Bases
14
Sources of the atoms of the pyrimidine ring
15
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16
DNA and RNA Degradation
17
Salvage Pathway for Purines (90)
Lesch-Nyhan Syndrome
18
Degradation of Purines (10)
19
Allopurinol Inhibits xanthine oxidase
X
X
20
Heme
21
Structure
22
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23
Porphyrias
24
hemoglobin
globin
heme
Fe (reutilized)
degraded (bilirubin)
free amino acids
25
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26
HYPERBILIRUBINEMIA
-- 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)
27
HYPERBILIRUBINEMIA 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.
28
Causes 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
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