Transdeamination And Metabolism Of Ammonia And Urea Flashcards
What is transamination?
Transfer of an amino group from an α-amino acid to an α-keto acid.
Main site is the liver; all amino acids undergo transamination except Lysine, Threonine, Proline, Hydroxyproline.
What acts as a coenzyme in transamination?
Pyridoxal phosphate.
It acts as an intermediate carrier of the amino group.
Name three examples of transaminases.
- Alanine transaminase (ALT)
- Aspartate transaminase (AST)
- Glutamate transaminase
These enzymes are crucial for transamination reactions.
What are the normal plasma levels of ALT and AST?
Low.
Elevated levels indicate liver or heart diseases.
What is the main site for deamination?
Liver and kidney.
Deamination involves the removal of an amino group from an amino acid.
What is oxidative deamination?
Glutamate is oxidized to α-ketoglutarate, releasing NH₄⁺.
It is one type of deamination.
What enzyme is involved in transdeamination?
L-glutamate dehydrogenase.
It converts glutamate into NH₃ and α-ketoglutarate.
What are the sources of ammonia in the body?
- Breakdown of amino acids
- Glutamine metabolism in kidney/intestine
- Amines (Histamine, Catecholamine)
- Purine/Pyrimidine breakdown
- Bacterial action on urea in the intestine
These sources contribute to ammonia levels in the body.
What are the three main fates of ammonia?
- Converted into urea for excretion
- Trapped as glutamine in liver, brain, kidney
- Directly excreted in urine
Ammonia is toxic to the brain, so its levels must be regulated.
What is hyperammonemia?
Excess ammonia leading to neurological toxicity.
Symptoms include tremors, slurred speech, blurred vision, confusion, coma, death.
What are the types of hyperammonemia?
- Hereditary: Genetic enzyme deficiencies in the urea cycle
- Acquired: Liver disease, renal failure
Each type has different underlying causes.
How does excess ammonia affect ATP production?
Decreases due to Kreb’s cycle inhibition.
This is a mechanism of ammonia toxicity.
Where does the urea cycle occur?
Liver.
Urea is then transported to the kidney for excretion.
What are the two nitrogen sources for the urea cycle?
- Ammonia
- Aspartate
These sources are crucial for urea synthesis.
What is the rate-limiting enzyme of the urea cycle?
Carbamoyl phosphate synthetase-1 (CPS1).
It is regulated by N-acetylglutamate.
What happens to urea in kidney failure?
Plasma urea increases, leading to hyperammonemia.
This condition requires careful management.
What treatment can be used for hyperammonemia due to kidney failure?
Neomycin.
This antibiotic kills urease-producing bacteria.
True or False: Liver failure results in decreased urea production and increased blood ammonia.
True.
This is a critical consequence of liver dysfunction.
What is the main site of transamination
Liver
Which amino acids do not undergo transamination
Lysine
Threonine
Proline
Hydroxyproline
What is the catalyst in transamination
Transaminases
Explain pyroxidal phosphate in transamination
Explain the clinical significance of serum transaminase
Define deamination
