Chapter 18: Amino Acid Oxidation and the Production of Urea - PowerPoint PPT Presentation

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Chapter 18: Amino Acid Oxidation and the Production of Urea

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Which AAs are ketogenic only? Glucogenic only? Both? Amino acid catabolism ... RED carbons: ketogenic. BLUE carbons: glucogenic. a-Ketoglutarate. Succinyl-CoA ... – PowerPoint PPT presentation

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Title: Chapter 18: Amino Acid Oxidation and the Production of Urea


1
Chapter 18 Amino Acid Oxidation and the
Production of Urea
  • Dr. Clower
  • CHEM 4203

2
Amino acids
  • Sources
  • Dietary protein
  • Biosynthetic
  • Essential vs. nonessential
  • Storage
  • Metabolism of amino acids
  • Amino acids as fuel
  • Degradation of cellular proteins
  • Diet rich in protein
  • Lack of carbohydrates

3
Amino acid catabolism
4
Amino group catabolism
5
Processes involved
  • Degradation of dietary protein to form amino
    acids
  • Transfer of amino group from amino acids to
    a-ketoglutarate
  • Glutamine transports ammonia from bloodstream
  • Alanine transports ammonia from muscle
  • Glutamate releases amino group as ammonia

6
1. Protein degradation
  • Polypeptides are continuously synthesized and
    degraded
  • Peptidases/proteases
  • Exopeptidase
  • Endopeptidase

7
Degradation of dietary proteins
8
2. Transfer of amino group
  • Transamination reaction
  • Enzyme transaminase or aminotransferase

9
Pyridoxal phosphate coenzyme
10
PLP reactions at a carbon
11
3. Glutamine transports ammonia from bloodstream
12
4. Alanine transports ammonia from muscle
  • Glucose-alanine cycle

Glu oxaloacetate ?-ketoglutarate
Asp
13
5. Glutamate releases amino group as ammonia
  • Oxidative deamination
  • L-glutamate dehydrogenase
  • Transdeamination
  • Transamination and deamination

14
NextNitrogen excretion
  • What is the fate of the ammonia in the liver
    mitochondria?
  • Recycle for use in biosynthesis
  • Excrete
  • Ammonotelic organisms
  • Ureotelic organisms
  • Uricotelic organisms
  • Plants
  • Ureotelic organisms urea cycle

15
Urea cycle
16
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17
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18
Nitrogen-acquiring reactions
19
What is the overall reaction for the urea cycle?
  • Energetic cost of urea cycle offset by
  • production of NADH in TCA (regeneration of
    oxaloacetate from fumarate)
  • production of NAD(P)H from oxidative deamination
    of glutamate

20
Aspartate-argininosuccinate shunt
21
Regulation of urea cycle
22
So far
23
Amino acid catabolism
  • What happens to the carbon skeleton?
  • How does amino acid catabolism yield energy?
  • 20 catabolic pathways converge to form 7 products
  • Pyruvate
  • a-ketoglutarate
  • Succinyl-CoA
  • Fumarate
  • Oxaloacetate
  • Acetyl-CoA
  • Acetoacetyl-CoA
  • Glucogenic vs. ketogenic

24
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25
Summary of amino acid catabolism
26
Which AAs are ketogenic only? Glucogenic only?
Both?
27
Amino acid catabolism
28
Cofactors in amino acid catabolism
  • Transfer of one-carbon units
  • Cofactors
  • Biotin
  • Tetrahydrofolate
  • S-Adenosylmethionine
  • Biotin

29
Cofactors in amino acid catabolism
  • Tetrahydrofolate

30
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31
Cofactors in amino acid catabolism
  • S-Adenosylmethionine
  • aka SAM
  • aka adoMET

32
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33
Amino acid catabolism
34
Pyruvate
35
Acetyl-CoA, acetoacetyl-CoA and fumarate
RED carbons ketogenic BLUE carbons glucogenic
36
a-Ketoglutarate
37
Succinyl-CoA
38
Oxaloacetate
39
Branched-chain amino acid catabolism
40
End of Chapter 18
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