Dhristi JEE 2022-24

What is Deamination of Amino Acids?

The process of removing an amino group from a molecule is called deamination, when the amino group is changed into ammonia. The enzyme that stimulates this action is called deaminases. Deamination principally occurs in the liver; however, glutamate is also deaminated in the kidney. The dissimilation of amino acids generates nitrogen-containing amino groups (NH2), which are harmful to cells. Through deamination, the liver alters these products into nontoxic ones. The amine group is first changed into ammonia (a toxic substance), subsequently to urea which is dispersed through urine.


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Deamination of Amino Acid 

Intake of proteins produces excess amino acid in the gastrointestinal tract, which needs to be excreted. In the liver, the amino acid is converted to ammonia soluble in water to form alkaline fluid, which is toxic through deamination. This toxic substance is converted to urea for safe excretion. The protease enzyme breaks down the digested protein into amino acids in the small intestine and stomach. After the conversion of excessive amino acid into urea, it is transported to the kidney via the bloodstream, where the blood is filtered, and urea is excreted through urine. The answer to what is deamination is the breakdown of amino acids into ammonia.


Types of Deamination

Below are the types of deamination.

Non-oxidative Deamination

In nonoxidative deamination, the amine group is removed without the oxidation process. A byproduct of non oxidative deamination is ammonia, producing consequent a-keto acids. Hydroxyl acids with one or more hydroxyl groups undergo non oxidative deamination. These amino acids do not take part in protein synthesis, and some are serine, homoserine, and threonine. Two amino acids, threonine, and serine consist of an aliphatic hydroxyl group that is one atom of hydrogen linked to another atom of oxygen represented as –OH.

The enzymes stimulating the non oxidative deamination are amino acid dehydratases. Pyridoxal phosphate acts as a coenzyme for non oxidative deamination reactions. Cysteine and homocysteine are both semi-essential amino acids (AA) as they can be acquired from diet converts into ammonia, hydrogen sulfide, and pyruvate in non oxidative deamination. Sulph Hydratases enzymes play a vital role in non oxidative deamination.


Oxidative Deamination

There are two types of deamination, non oxidative and oxidative deamination. This process breaks down the excess protein from the diet by removing the amino group from amino acids. Both deamination reactions are catalyzed by enzymes. Additionally, both reactions produce ammonia corresponding to a-keto acids. 

Oxidative deamination mostly occurs in the liver and kidney, producing a-keto acids and other oxidized products from amine-enriched compounds. At the same time, non oxidative deamination produces nitrogen-enriched ammonia without undergoing oxidation. The occurrence of oxidative deamination is restricted to the kidney and liver, whereas non oxidative deamination occurs in other organs. Amino acid dehydratases enzyme mainly stimulates non oxidative deamination; on the other hand, glutamate dehydrogenase is the primary enzyme responsible for oxidative deamination. Oxidation is the key difference between oxidative and non-oxidative deamination; coenzymes play a significant role in the oxidation reaction, while coenzymes such as pyridoxal phosphate trigger nonoxidative deamination.


Transamination and Deamination

Transamination and deamination shows the difference between transamination and deamination. Transamination refers to a process of transfer of one amino group from one molecule to another, particularly from an amino acid to a keto acid. Whereas in deamination, an amino group is removed from an amino acid or other compounds. In the process of deamination, excess protein is converted into ammonia, then to urea; on the other hand, in transamination, the synthesis of nonessential amino acids takes place. Transamination takes place in every cell of the body, but deamination happens in the liver. 

The main byproduct of transamination is glutamic acid, a nonessential enzyme that helps neurons in the brain to send and receive information. Glutamic acid is the most abundant neurotransmitter invertebrate nervous system. It is used to form protein and then turns into glutamate. Transamination is a reversible process, while deamination is unalterable. In the transamination biochemical process, an amino group is transferred to a keto group; in the biochemical deamination process, excess protein breakdown in the liver releases ammonia.


Conclusion

In case of excess protein intake, deamination breaks down the amino acid into ammonia for energy. An enzyme that stimulates this biochemical reaction is called deaminases. This process allows the body to use excess amino acids into useful byproducts. Ammonia is a toxic substance that is converted to urea or uric acids by enzymes. The remaining amino acid consisting mainly of hydrogen and carbon is oxidized for energy. There are two forms of deamination; non-oxidation and oxidation.

FAQs on Deamination

1. What is an amino acid?

Amino acid molecules combine to form proteins; both are building blocks of life. While digestion of protein, the amino acid is liberated. The body uses the synthesis amino acid to make protein. Amino acid is classified under three categories; essential, nonessential, and conditional amino acid. Essential amino acid is not synthesized in the body; food is the only source. There are nine essential amino acids. Nonessential amino acids are produced in the body; an external source is not needed to produce them. Conditional amino is used during stress or disease; these include proline, serine, glutamine, tyrosine, arginine, ornithine, and cysteine. Amino acids are organic molecules containing an anime group, an acidic carboxyl group, and an organic side chain specific to each amino acid.

2. What are the differences between enzyme and protein?

Protein and enzymes are closely related hence confused many times. The enzyme is a specific type of protein with a discrete function. Enzymes regulate various biochemical functions; from this prospect, it is solely functional. But protein can be either functional or structural. Hence all enzymes can be categorized as globular protein, but all proteins are not globular. Proteins consist of polymers of amino acids, the structural and functional building blocks of all living beings; they are macromolecules. The key difference is enzymes are the catalyst to biochemical reaction, while proteins have multiple functions such as the formation of structure, storage, transpiration, regulation, and stimulation of biological processes.

3. What is the ornithine cycle?

Ammonia is a toxic byproduct of nitrogen metabolism, which needs to be eliminated from the body. The ornithine or urea cycle transforms excess ammonia into urea at mitochondria cells in the liver. The urea seeps into the bloodstream is filtered by the kidney and is ultimately excreted through urine. The urea cycle is a sequence of five reactions triggered by several enzymes. The first two steps occur at the mitochondrial matrix, and the following three steps occur at cytosol. Thus two cellular compartments of the liver are involved in the ornithine cycle. The primary function of the urea cycle is to excrete an excessive amount of ammonia from the body. A healthy adult emits around ten to twenty grams of ammonia per day.

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