Amino Acids: Disposal of Nitrogen

What is the first step in the catabolism of most amino acids?

What is the primary source of amino acids in the amino acid pool?

Which enzyme is primarily involved in the process of transamination?

Which process primarily involves the removal of ammonia from amino acids?

Which coenzyme is required by all aminotransferases?

How does the body dispose of nitrogen from amino acids?

In which organs does oxidative deamination primarily occur?

What are the three pathways utilized by the amino acid pool?

What role does ammonia play in amino acid catabolism?

What role do digestive proteases play in amino acid metabolism?

Which substance acts as an allosteric inhibitor of glutamate dehydrogenase?

What happens to excess amino acids in the body?

Which amino acids do not participate in transamination during their catabolism?

What is the primary function of the reactions involved in oxidative deamination?

Which of the following is NOT a source of the amino acid pool?

Which term describes the process of transferring an amino group from one amino acid to a keto acid?

Disposal of Nitrogen in Amino Acids

Amino acids are not stored in the body; they are sourced from diet, newly synthesized, or derived from protein degradation.
Excess amino acids are rapidly degraded to prevent accumulation.

Amino Acid Pool

The amino acid pool consists of free amino acids available throughout the body, sourced from:
- Degradation of body proteins
- Dietary protein intake
- Synthesis of nonessential amino acids from metabolic intermediates
The amino acid pool serves three purposes:
- Synthesis of body proteins
- Precursor for nitrogen-containing small molecules
- Conversion to glucose, glycogen, fatty acids, or CO2

Digestion of Dietary Proteins

Amino acid catabolism is integrated into nitrogen metabolism.
Dietary proteins are primary sources of nitrogen.
Nitrogen excretion occurs as urea, ammonia, and other products from amino acid metabolism.

Amino Acid Catabolism: Removal of Nitrogen

Transamination

Transamination transfers the α-amino group of amino acids to α-ketoglutarate, forming α-ketoacids and glutamate.
Catalyzed by aminotransferases, present in cytosol and mitochondria of various cells.
All amino acids except lysine, threonine, and proline undergo transamination.
Aminotransferases require pyridoxal phosphate, a vitamin B6 derivative.

Oxidative Deamination

Primarily occurs in the liver and kidneys.
Produces α-keto acids for energy metabolism and ammonia for urea synthesis.
Glutamate dehydrogenase can use NAD+ or NADP+ as coenzymes; NAD+ is for oxidative deamination, while NADPH is for reductive amination.
GTP inhibits glutamate dehydrogenase, while ADP activates it.

Transport of Ammonia to the Liver

Ammonia generated from amino acid catabolism is transported to the liver for urea synthesis.

Summary

Proper digestion of proteins occurs in the small intestine through specialized enzymes.
The amino group is removed from free amino acids via transamination and oxidative deamination.
The process is essential to manage nitrogen waste and maintain amino acid balance in the body.

This quiz focuses on how the body handles amino acids, specifically the processes of transamination and oxidative deamination. Dive into key concepts such as the amino acid pool and ammonia exchange among tissues. Gain a clearer understanding of amino acid metabolism and its implications for cellular function.