Spectrophotometric Measurement of Transamination

In a previous publication (1) from this laboratory, it was demonstrated that the transamination of amino acids to a-ketoglutaric acid is a reaction of wide scope. Although the data reported in the earlier paper permitted the computation of Q transaminase values, these values were of limited quantitative significance since no attempt was made to study the kinetics of these reaction systems, the emphasis being placed on the determination of the scope and validity of the reaction. It therefore seemed important to secure kinetic data in order to permit proper evaluation of the role of these enzymes in metabolic systems. Because some of the transaminases in crude extracts appeared very weak, and because of the limits of accuracy of the manometric method employed in the earlier study (l), a sensitive, acuurate method of assay was required. Green, Leloir, and Nocito (2) originally suggested a possible method for the spectrophotometric assay of transaminase activity. A procedure, employing this principle, as well as some rates of transamination determined by its use, is presented here.