Title: Chapter 18: Amino Acid Oxidation and the Production of Urea
1Chapter 18 Amino Acid Oxidation and the
Production of Urea
2Amino 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
3Amino acid catabolism
4Amino group catabolism
5Processes 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
61. Protein degradation
- Polypeptides are continuously synthesized and
degraded - Peptidases/proteases
- Exopeptidase
- Endopeptidase
7Degradation of dietary proteins
82. Transfer of amino group
- Transamination reaction
- Enzyme transaminase or aminotransferase
9Pyridoxal phosphate coenzyme
10PLP reactions at a carbon
113. Glutamine transports ammonia from bloodstream
124. Alanine transports ammonia from muscle
Glu oxaloacetate ?-ketoglutarate
Asp
135. Glutamate releases amino group as ammonia
- Oxidative deamination
- L-glutamate dehydrogenase
- Transdeamination
- Transamination and deamination
14NextNitrogen 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
15Urea cycle
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18Nitrogen-acquiring reactions
19What 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
20Aspartate-argininosuccinate shunt
21Regulation of urea cycle
22So far
23Amino 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
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25Summary of amino acid catabolism
26Which AAs are ketogenic only? Glucogenic only?
Both?
27Amino acid catabolism
28Cofactors in amino acid catabolism
- Transfer of one-carbon units
- Cofactors
- Biotin
- Tetrahydrofolate
- S-Adenosylmethionine
- Biotin
29Cofactors in amino acid catabolism
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31Cofactors in amino acid catabolism
- S-Adenosylmethionine
- aka SAM
- aka adoMET
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33Amino acid catabolism
34Pyruvate
35Acetyl-CoA, acetoacetyl-CoA and fumarate
RED carbons ketogenic BLUE carbons glucogenic
36a-Ketoglutarate
37Succinyl-CoA
38Oxaloacetate
39Branched-chain amino acid catabolism
40End of Chapter 18