Transamination and its features

  • The chemical process in which there is transfer of an amino (-NH2) group from an amino acid to a keto-acid is known as transamination.
  • This process involves the inter conversion of a pair of amino acids and a pair of keto acids which are catalyzed by a group of enzymes called transaminases (recently called aminotransferases).

Salient features of Transamination

  • All transaminases require pyridoxal phosphate (PLP) which is a co-enzyme derived from vitamin B6.
  • There are specific transaminases that exist for each pair of amino and keto acids. However, only two namely, aspartate transaminase and alanine transaminase make a significant contribution for transamination.
  • There is no free NH3 liberated but only the transfer of a amino group occurs.
  • Transamination is reversible.

Amino acid metabolism Metabolism of amino acids differs, but 3 common  reactions: Transamination Deamination Decarboxylation. - ppt download

                                                                               Imagesource: slideplayer

  • Transamination is very important for the re-distribution of amino groups and production of non-essential amino acids as per the requirement of the cell which involves both catabolism and anabolism of amino acids.
  • Transamination helps to divert the excess amino acids towards energy generation.
  • The amino acids undergo transamination so that it can finally concentrate nitrogen in glutamate.
  • Glutamate is the only amino acid that undergoes oxidative deamination to a significant extent to liberate free NH3 that is used for urea synthesis.
  • All amino acids participate in transamination (except lysine, threonine, proline and hydroxyproline).
  • Transamination is not restricted to α-amino groups only. δ- amino group of ornithine is transaminated.
  • Serum transaminases are important as they are used for diagnostic and prognostic purposes.

Mechanism of transamination

  • Transamination occurs in two stages. They are as follows:

a)Transfer of the amino group to the co-enzyme pyridoxal phosphate (bound to the co-enzyme) to form pyridoxamine phosphate.


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b)The amino group of pyridoxamine phosphate is then transferred to a keto acid to produce a new amino acid and the enzyme with PLP is regenerated.

  • All the transaminases require pyridoxal phosphate (PLP), a derivative of vitamin B6.
  • The aldehyde group of PLP is linked with ε- amino group of lysine residue, at the active site of the enzyme forming a Schiff base (imine linkage).
  • When an amino acid (substrate) comes in contact with the enzyme, it displaces lysine and a new Schiff base linkage is formed.
  • The amino acid-PLP-Schiff base tightly binds with the enzyme by non-covalent forces.
  • Snell and Braustein proposed a Ping Pong Bi Bi mechanism involving a series of intermediates (aldimines and ketimines) in transamination reaction.





Transamination and its features