New enzymatic methods for selective assay of l-lysine using an l-lysine specific decarboxylase/oxidase from Burkholderia sp. AIU 395

We developed new enzymatic methods for the selective assay of l-lysine by utilizing an oxidase reaction and a decarboxylation reaction by the l-lysine-specific decarboxylase/oxidase (l-Lys-DC/OD) from Burkholderia sp. AIU 395. The method utilizing the oxidase reaction of this enzyme was useful for determination of high concentrations of l-lysine. The method utilizing the decarboxylase reaction, which proceeded via the combination of the l-Lys-DC/OD and putrescine oxidase (PUO) from Micrococcus rubens, was effective for determination of low concentrations of l-lysine. Both methods showed good linearity, and neither was affected by other amino acids or amines. In addition, the within-assay and between-assay precisions of both methods were within the allowable range. The coupling of l-Lys-DC/OD with PUO was also useful for the differential assay of l-lysine and cadaverine. These newly developed methods were applied to the assay of l-lysine in biological samples and found to be effective.