Transamination and deamination in biological systems
Transamination is the transfer of an amine group from molecule A to molecule B. Reactant A contains an amine group (such as an amino acid) and B contains a keto (ketone) group. The amine and keto groups are basically switched between the molecules in the same place, and this is no easy feat. The activation energy for this reaction is really high and requires a cofactor or enzyme to catalyze the reaction. An amino acid and an alpha keto acid (amine, ketone) are input as products, and a second, different keto acid is formed, and a different amino acid.
Transamination in biological pathways can be used to degrade essential amino acids to nonessential amino acids. This is one way the body creates these amino acids. This reaction is catalyzed by enzymes called aminotransferases or transaminases. One pathway to do this in biological systems is the deamination of amino acids using an enzyme PLP ( pyridoxyl-5'-phosphate ). This is a three step process that shifts the amine group from the mino acid --> PLP -> the keto acid. In step one, PLP picks up the amine group, from nucleophilic attack of the amine at the imine group, to become PMP ( pyridoxamine-5'-phosphate). In step two, PLP transfers it over to the other molecule through nucleophilic attack at the keto group. Keto carbons are delta positive and the electron pair on an amine group will readily attack a ketone. Step three consist of a hydrolysis. Water is used to hydrolyze the imine bond to release the New amino acid.
The products are always an alpha keto acid of the skeleton of the input amino acid (only amine group changed to keto group) and an amino acid dependent on the alpha keto acid we began with as input. The input alpha keto acid will determine the amino acid as output and is usually alanine, aspartate, or glutamate, but sometimes other amino acids as well
