Determination of branched-chain L-amino acids and their keto analogs with leucine dehydrogenase.

Abstract

The simple and sensitive spectrophotometric method for determination of branchedchain L-amino acids and their keto analogs with leucine dehydrogenase (EC 1.4.1.9) is described. Branched-chain L-amino acids were determined with the enzyme by measuring the formation of NADH spectrophotometrically. A linear relationship was established between the absorbance at 340nm and the concentration of the amino acid (0.02_??_0.20 μmol). The determination of branched-chain keto acids (0.01_??_0.12 μmol) is based on the measurement of NADH disappeared. This method can be used to assay D-amino acid aminotransferase (EC 2.6.1.21), and is applicable to the assay of other enzymes catalyzing the formation or decomposition of branched-chain L-amino acids and their keto analogs as well.