transamination

Aminotransfer reaction between an amino acid and an alpha-keto acid

There are two chemical reactions known as transamination (or aminotransfer). The first is the reaction between an amino acid and an alpha-keto acid. The amino group is transferred from the former to the latter; this results in the amino acid being converted to the corresponding α-keto acid, while the reactant α-keto acid is converted to the corresponding amino acid (if the amino group is removed from an amino acid, an α-keto acid is left behind).

Transamination in biochemistry is accomplished by enzymes called transaminases or aminotransferases. The human body synthesizes the 11 non-essential amino acids and transamination is the process by which most of these syntheses occur. The other 9 must be supplied in the diet. The chirality of an amino acid is determined during contamination. This reaction uses the coenzyme PLP, and has been shown to be a kinetically perfect reaction. The product of transamination reactions depend on the availability of alpha-keto acids. The products usually are either alanine, aspartate or glutamate, since their corresponding alpha-keto acids are produced through metabolism of fuels.

The second type of transamination reaction, which can be described as a nucleophilic substitution of one amine or amide anion on an amine or ammonium salt.^[1] For example, the attack of a primary amine by a primary amide anion can be used to prepare secondary amines:

RNH₂ + R'NH⁻ → RR'NH + NH₂⁻

Symmetric secondary amines can be prepared using Raney nickel (2RNH₂ → R₂NH + NH₃). And finally, quaternary ammonium salts can be dealkylated using ethanolamine:

R₄N⁺ + NH₂CH₂CH₂OH → R₃N + RN⁺H₂CH₂CH₂OH

Ser and Thr are the only two amino acids that do not always undergo transamination.

See also

• Transaminase

References

1. ^ Smith, M. B. and March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 5th ed. Wiley, 2001, p. 503. ISBN 0471585890

External links

• Overview of amino acid synthesis
• The chemical logic behind aminoacid degradation and the urea cycle