Thermostabilization of porcine kidney D ‐amino acid oxidase by a single amino acid substitution

D ‐amino acid oxidase (DAO) is of considerable practical importance, such as bioconversion and enzymatic assay. In this study, we succeeded in obtaining a thermostable mutant DAO from porcine kidney by a single amino acid substitution. This mutant enzyme, F42C, was stable at 55°C, while the wild‐type enzyme was stable only up to 45°C. The K m values of F42C for D ‐amino acids was about half of those of the wild‐type enzyme. This mutant DAO with improved stability and affinity for its substrates is advantageous for the determination of D ‐amino acids. © 2005 Wiley Periodicals, inc.