Enzymatic determination of d-alanine with l-alanine dehydrogenase and alanine racemase

An enzymatic assay system of D-Ala, which is reported to affect the taste, was constructed using alanine racemase and L-alanine dehydrogenase. D-Ala is converted to L-Ala by alanine racemase and then deaminated by L-alanine dehydrogenase with the reduction of NAD(+) to NADH, which is determined with water-soluble tetrazolium. Using the assay system, the D-Ala contents of 7 crustaceans were determined.