Amino Acid Metabolism and Urea Cycle

Amino Acid Metabolism and Urea Cycle

• Nutritionally nonessential amino acids are synthesized in the body.

Amino Acid Catabolism

• Amino acids are catabolized through three general processes:
  • Specific catabolic pathways
  • Conversion to other amino acids, which are then catabolized
  • Transamination plus deamination (transdeamination)

Nonessential Amino Acid Biosynthesis

• Nonessential amino acids can be formed from:
  • Essential amino acids
  • Nonessential amino acids
  • Metabolic intermediates

Transamination

• Alanine aminotransferase reaction involves the transfer of an amino group from alanine to α-ketoglutarate, forming pyruvate and glutamate.

Deamination

• Direct oxidative deamination of L-Glutamate occurs through glutamate dehydrogenase.
• Glutamate dehydrogenase is regulated allosterically.

D-Amino Acids

• D-Amino acids are found in plants and cell walls of microorganisms, but not used in mammalian protein synthesis.
• D-Amino acids are present in the diet and are metabolized by kidney and liver.

Amphibolic Intermediates

• Amphibolic intermediates are formed from the carbon skeletons of amino acids.
• Examples include:
  • Transamination of an amino acid with α-ketoglutarate
  • Direct oxidative deamination of glutamate by glutamate dehydrogenase

Urea Cycle

• Carbamoyl phosphate is synthesized and enters the urea cycle.
• The urea cycle is a critical pathway for removing ammonia from the body.

This quiz covers the general principles of amino acid metabolism, including the synthesis of nutritionally nonessential amino acids and the three general processes of amino acid catabolism.