University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

371

Pages:

6
Author:

Sheha A.

Protein Catabolism In humans, the dietary proteins are digested to their constituent amino acids in the gastrointestinal tract by the action of various enzymes. The resulting mixture of free amino acids is transported into the epithelial cells of the small intestine. These are absorbed into the blood capillaries and travel to the liver. The catabolism of amino acids is a two-step process: Transamination and Deamination. Transamination: Transamination is the process by which the α-amino group of an amino acid is transferred to an α-keto acid, resulting in the formation of a new amino acid and a keto acid. Transamination reactions are catalyzed by aminotransferases or transaminases. In this transamination reaction, the α-amino group of the α-amino acid is transferred to α-ketoglutarate, resulting in the formation of α-keto acid and glutamate. Transamination In transamination, the α-amino group of an amino acid is transferred to an α-keto acid, resulting in the formation of a new amino acid and a keto acid. This reaction is catalyzed by aminotransferases, which require pyridoxal phosphate as a cofactor. Deamination Deamination is the removal of the amino group from an amino acid. It is also called oxidative deamination. It takes place in two steps: Oxidation: The amino acid is oxidized by amino acid oxidase to form an α-imino acid. Hydrolysis: A water molecule is added to the α-imino acid, which decomposes to form the corresponding α-keto acid and ammonia. Urea Cycle Amino acid nitrogen is excreted as urea. Excess nitrogen is converted to urea in the liver. Urea is then transported to the kidney and is excreted. Urea is less toxic than ammonia. In ureotelic organisms, ammonia is deposited as urea. The Liver is converted into urea in the Urea Cycle The process takes place in the liver. The excess nitrogen is converted into urea. Urea is then excreted into the kidneys and is excreted.