Transamination

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. This process is an important step in the synthesis of some non-essential amino acids (amino acids that are not supplied from the diet). The chirality of an amino acid is determined during transamination. 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.

Lysine and threonine are the only two amino acids that do not always undergo transamination.

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. 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