Transamination; Urea Cycle; Oxidation of ?-Keto Acids - PowerPoint PPT Presentation

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Transamination; Urea Cycle; Oxidation of ?-Keto Acids

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... Oxidation of -Keto Acids. Catabolism: The Big Picture ... AA Catabolism Via Citric Acid Cycle. Amino acid degradation. One of seven metabolic intermediates ... – PowerPoint PPT presentation

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Title: Transamination; Urea Cycle; Oxidation of ?-Keto Acids


1
Lecture 12
  • Transamination Urea Cycle Oxidation of ?-Keto
    Acids

2
Catabolism The Big Picture
3
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4
Transamination General Reaction (Liver)
O
COO
C
COO
PLP


O
C
COO
COO
5
Pyridoxal Phosphate in Transamination
O
H
O
C
HO
O
P
O
O
6
?-KG in Transamination
7
Transamination
8
Why pyridoxal phosphate?
Electron sink that stabilizes intermediate
9
PLP General Role in AA Metabolism
Decarboxylases
R
CH
COO
NH
Transaminase
CH
  • Forms Schiff base
  • Stabilizes intermediates (electron sink)

10
Glutamate Dehydrogenase
11
Glutamine Transport of Ammonia
12
Transport of amino groups
13
Disposal of NH4 in Mammals
  • NH4 is toxic amino acids are not

Tissues Liver (mitochondria and cytosol)
Transamination pyruvate?alanine ?-KG?glutamate Glu
tamine synthesis Glutamate NH4? Glutamine
Urea
14
Urea Cycle Summary
15
Synthesis of Carbamoyl Phosphate
16
Synthesis of Carbamoyl Phosphate
17
Urea Cycle
O
O
C
O
P
O
C
O

O
NH
CH
CH
COOH
COOH
Ornithine
Citrulline
18
Urea Cycle-Argininosuccinate synthetase
NH
COOH
O
C
C
CH
COOH
ATP
NH
NH
CH
COOH
AMP
COOH
Aspartate
CH
CH
COOH
COOH
Argininosuccinate
Citrulline
19
Urea Cycle-Argininosuccinate Lyase
20
Urea Cycle-Arginase
21
Regulation of Urea Cycle
22
AA Catabolism Via Citric Acid Cycle
23
Amino acid degradation
  • One of seven metabolic intermediates
  • Glucogenic
  • Pyruvate
  • ?-ketoglutarate
  • Succinyl-CoA
  • Fumarate
  • Oxaloacetate
  • Ketogenic (Leucine)
  • Acetyl CoA or acetoacetate

24
Amino acid degradation
  • C3 converted to pyruvate
  • C4 converted to oxaloacetate
  • C5 converted to a ketoglutarate
  • Branched oxidative decarboxylation
  • Met, Trp, Phe, and Tyr are precursors for
  • cofactors, hormones.

25
C3 family is converted to pyruvate
26
Glycine degradation
Serine hydroxymethyl transferase

One carbon transfer is important.
Pyruvate
27
Tetrahydrofolate and 1-Carbon Transfer
H
N
Glutamate
H
H
O
5
HN
10
C
CH
COO
O
Pteridine
COO
Can transfer C in several oxidation states
Methyl, methylene, formyl, etc.
28
1 Carbon carriers
29
Various Oxidation States
30
Various Oxidation States
31
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