how amino acids are synthesisd in the cell?

Dear Student,

 Living organisms such as plants and many microorganisms can synthesize all 20 standard amino acids.  But, other organisms such as mammals and other animals can synthesise 12 non essential amino acids  and remaining 8 essential amino acids must be obtained from the diet.

Nitrogen in the form of ammonia is the source of nitrogen for all the amino acids.

Ammonium ions are incorporated into amino acids.

 Two amino acids glutamate and glutamine provide the critical entry point.

Amino acids are synthesised in the cell mainly through two principal ways;

i) Reductive amination

ii) Transamination

i) Reductive amination − glutamate is formed from NH4⁺ by the reaction with α-ketoglutaric acid.

 α -ketoglutaric acid + NH4⁺ + NADPH → Glutamate + H₂O + NADP

This reaction is catalyzed by Glutamate dehydrogenase.

This reaction ocur in mitochondria.

ii) Transamination − transfer of the amino group from one amino acid to the keto group of the ketoacid, catalyzed by the enzyme transaminase.This enzyme is found within both the cytoplasm and mitochondria. 

E.g., formation of amides, asparagine and glutamine from amino acids, aspartic acid and glutamic acid, by the addition of another amino group to each.

Transamination reaction participate in the synthesis of most amino acids. Glutamatic acid is the source of amino group (NH₂) for most other amino acids through transamination reaction.