Non-Biological Transamination

Deamination of amino acids by carbonyl compounds has long been known in organic chemistry. Classical instances are the Strecker reaction of amino acids with alloxan and rimilar reactions with o-quinones, isatin, ninhydrin, methylglyoxal, and the like. In such cases deamination is usually associated with decarboxylation of the amino acid. Condensation of the amino and carbonyl groups to yield SchiiTs bases, and tautomeric transformation of these, are generally assumed as intermediary steps. 

Formation of Sebiff s bases is also postulated in the ease of decaibo lation at keto acids by amino compounds (Langenbeek s artificial carboxylases). Recently bacterial amino acid decarboxylases have also been shown to contain an active carbonyl in their prosthetic component—phosphorylated pyridoxal (84).i 

In 1934, Herbst and Engel (92) found that, in boiling aqueous solutions, the NHj— group of o-amino acids is transferred to o-keto acids, a new 

In many instances, the aldehyde Ri CHO, corresponding to the oiis al keto acid, is formed in addition to the aldehyde Ri CHO, resulting from breakdown of the initial amino add. The reaction mechanism is pictured as follows (Herbst, 91)  

The rate of non biological transamination is highest with aromatic a-amino acids or cystine, t.e., with substrates inactive in enzymatic transamination (89). On the other hand, the dicarboxylic amino and a-keto acids react slowly in this model system (88, 91), whereas their participation is obligatory in enzymatic transamination (34,23). 

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