Amino acid metabolism Flashcards
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Nitrogen pool
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Tissue protein
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Urea cycle
Transamination
Exchange of an amine group with a ketone group from another molecule
- Catalysed by transaminases
What is the most frequent keto-acid involved in transamination?
Alpha-ketoglutaric acid
Give an example of a transamination reaction
Alanine + alpha-ketoglutaric acid → Pyruvic acid + Glutamic acid
Structure: Alanine
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Structure: α-ketoglutarate/α-ketoglutaric acid
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Structure: Pyruvic acid/Pyruvate
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Structure: Glutamic acid
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When is transamination seen?
During amino acid synthesis
What are the ‘collection’ and ‘receiving’ agents for nitrogen?
- α-ketoglutarate
- Glutamic acid
List some transaminases
- ASAT=GOT
- ALAT=GPT
Location of ASAT=GOT
In the cytosol/mitochondrion of:
- Liver
- Heart
- Muscle
Location of ALAT=GPT
In the cytosol/mitochondrion of:
- Liver
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Ketoglutaric + Glutamic acid
Synthesis of amino acids and other nitrogen bases
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Nitrogen bases
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Transamination
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Transamination
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Amino acid
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Ketoacid
Cysteine is synthesised from…
- Methionine
- Serine
Glycine is synthesised from…
Phosphoglyceric acid
Which amino acids are essential in the chicken?
- Glycine
- Arginine
Give the relevance of essential amino acids in ruminants
Ruminants have no essential amino acids
They are produced by rumen microbes
Oxidative deamination
Amino acid → Keto acid
- Removal of amine functional group (NH3)
- Amin functional group is replaced by the ketone group
Oxidative deamination occurs primarily on…
Glutamic acid
Glutamate dehydrogenase is allosterically controlled by…
- ATP (Inhibitor)
- ADP (Activator)
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Oxidative deamination
Once keto acids have been formed, they can be used for…
Metabolism into CO2 + H2O
Via Citric acid cycle
Amino acids converted into acetyl-CoA can be converted into…
Ketone bodies
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The fate of Amino acid carbon skeletons
Amino acids producing pyruvate
- Alanine
- Glycine
- Cysteine
- Serine
Amino acids producing acetyl-CoA
- Isoleucine
- Leucine
- Tryptophan
Amino acids producing oxaloacetate
- Aspartic acid
- Asparagine
Amino acids producing fumarate
- Tyrosine
- Phenylalanine
- Aspartic acid
Amino acids producing succinyl-CoA
- Isoleucine
- Methionine
- Threonine
- Valine
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Acetoacetyl CoA
Amino acids producing acetoacetyl-CoA
- Leucine
- Lysine
- Phenylalanine
- Tyrosine
Amino acids producing α-ketoglutarate
- Glutamic acid
- Glutamine
- Histidine
- Proline
- Arginine
Ammonia is produced via…
- Oxidative deamination
- Degradation of biogenic amines
- Absorption from the GI tract
Ammonia is detoxified via…
- Urea cycle
- L-Glu synthesis
- Gln + Asn synthesis
- Kidney: Glutaminase activity
- Purine synthesis: Uric acid (Birds)
Which species lack the urea cycle?
Birds
They do not possess the arginase enzyme
Portosystemic Shunt
- Blood of portal vein enters the vena cava, not the liver
- Ammonia toxicosis risk
- Seen in Yorkshire terrier
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Glutamine synthesis + Degredation
Reaction: Decarboxylation of amino acids
Amino acid → Amine
Amino acid decarboxylase
Decarboxylation of Histidine
Histidine → Histamine
Histidine decarboxylase
Decarboxylation of Tyrosine → Catecholamines
Tyrosine → DOPA → Catecholamines
Dihydroxyphenylalanine (DOPA) decarboxylase
Decarboxylation of Tyrosine
Tyr → Tyramine
Tyrosine decarboxylase
Decarboxylation of: 5-OH-Trp
5-OH-Trp → Serotonin
5-OH tryptophane decarboxylase
Decarboxylation of Glutamate
Glutamate → Gamma-amino-butyrate (GABA)
Glutamate decarboxylase
Decarboxylation of: Serine
Serine → Ethanolamine (Cholamine)
Serine decarboxylase
Decarboxylation of: Cysteine
Cysteine → Cysteamine
Cys-decarboxylase
Decarboxylation of: Cysteine → Taurine
Cysteine → cysteic acid → Taurine
Decarboxylation of Aspartic acid
Aspartic acid → Beta-alanine
Asp-decarboxylase
What is the role of taurine in bile salt synthesis?
Bile acids are conjugated with taurine to produce bile salts
Decarboxylation of: Ornitine
Ornitine → Putrescine
Ornithine-decarboxylation
Decarboxylation of: Lysine
Lysine → Cadaverine
Lysine-decarboxylase
Cadaverine
- Foul smelling
- Produced by protein hydrolysis during putrefaction
Location of carnosine
Muscle + Brain (Mammals)
Location of Anserine
Muscle + brain (birds)
The function of carnosine and anserine
Buffering lactic acid + RBCs
Function of glutathione
- Splits disulphide bonds of proteins (reduction)
- Reduces thioredoxine
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Glutathione removes peroxides via which enzyme?
Glutathione peroxidase