Amino Acid Degradation

Study Notes

Amino acid degradation is the process of breaking down amino acids into smaller molecules, which can be used for energy production or other cellular processes.
There are three main ways to degrade amino acids:
- Oxidative deamination: involves the removal of an amino group (-NH2) and the formation of an alpha-keto acid.
- Transamination: involves the transfer of an amino group to an alpha-keto acid, resulting in the formation of a new amino acid and an alpha-keto acid.
- Dehydrogenation: involves the removal of a hydrogen atom from the amino acid, resulting in the formation of an alpha-keto acid.

The urea cycle, also known as the ornithine cycle, is a metabolic pathway that converts ammonia (NH3) into urea, which can be excreted from the body.
The urea cycle takes place in the liver and kidney cells.
The cycle involves the following steps:
1. Ammonia (NH3) is converted into citrulline through the action of the enzyme N-acetylglutamate synthase.
2. Citrulline is converted into arginine through the action of the enzyme argininosuccinate synthase.
3. Arginine is converted into ornithine and urea through the action of the enzyme arginase.
4. Ornithine is recycled back into citrulline through the action of the enzyme ornithine transcarbamylase.

Transamination is a reaction in which an amino group (-NH2) is transferred from an amino acid to an alpha-keto acid, resulting in the formation of a new amino acid and an alpha-keto acid.
Transamination reactions are reversible and can occur in both directions.
Transamination reactions are catalyzed by enzymes called transaminases.
Examples of transamination reactions:
- Aspartate + alpha-ketoglutarate ⇌ oxaloacetate + glutamate
- Alanine + alpha-ketoglutarate ⇌ pyruvate + glutamate

Deamination is the process of removing an amino group (-NH2) from an amino acid, resulting in the formation of an alpha-keto acid.
Deamination reactions are irreversible and can occur in the liver, kidneys, and other tissues.
Deamination reactions are catalyzed by enzymes called deaminases.
Examples of deamination reactions:
- Glutamate → alpha-ketoglutarate + NH3
- Aspartate → oxaloacetate + NH3

Amino acid degradation is the process of breaking down amino acids into smaller molecules, which can be used for energy production or other cellular processes.
Three main ways to degrade amino acids: oxidative deamination, transamination, and dehydrogenation.

The urea cycle, also known as the ornithine cycle, converts ammonia (NH3) into urea, which can be excreted from the body.
The cycle takes place in the liver and kidney cells.
The cycle involves four steps:
- Ammonia (NH3) is converted into citrulline.
- Citrulline is converted into arginine.
- Arginine is converted into ornithine and urea.
- Ornithine is recycled back into citrulline.

Transamination is a reaction in which an amino group (-NH2) is transferred from an amino acid to an alpha-keto acid.
Transamination reactions are reversible and can occur in both directions.
Transamination reactions are catalyzed by enzymes called transaminases.
Examples of transamination reactions:
- Aspartate + alpha-ketoglutarate → oxaloacetate + glutamate
- Alanine + alpha-ketoglutarate → pyruvate + glutamate

Deamination is the process of removing an amino group (-NH2) from an amino acid, resulting in the formation of an alpha-keto acid.
Deamination reactions are irreversible and can occur in the liver, kidneys, and other tissues.
Deamination reactions are catalyzed by enzymes called deaminases.
Examples of deamination reactions:
- Glutamate → alpha-ketoglutarate + NH3
- Aspartate → oxaloacetate + NH3