meso-Diaminopimelate dehydrogenase (meso-DAPDH) catalyzes the reversible NADP + -dependent oxidative deamination of meso-diaminopimelate to produce L-2-amino-6-oxopimelate within cells. We screened thermostable meso-DAPDH in various thermophiles and found the enzyme in Ureibacillus thermosphaericus characterization of the enzyme, we succeeded in the creation of thermostable NADP + -dependent D-amino acid dehydrogenase (D-AADH) by introduction of five amino acid (Gln154Leu, Asp158Gly, Thr173Ile,

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... Arg199Met and His249Asn) substitutions into the substrate recognition site of meso D-AADH exhibited no activity toward meso-diaminopimelate, but it newly catalyzed the reversible NADP +dependent oxidative deamination of D-amino acids to 2-oxo acids. As the application of this enzyme, we developed the synthetic methods of D-branched-chain amino acids and their analogs labeled with stable isotopes such as 13 C and 15 N, and the simple and specific assay method for D-isoleucine. Moreover, we succeeded in the determination of 3D structures for meso-DAPDH apo form and NADP + /TES/meso-DAPDH ternary complex. These structural features revealed molecular mechanisms for both the high thermostability and NADP + -recognition of U. thermosphaericus meso-DAPDH. In addition, the structural analyses of the active site architectures gave us the information about the molecular mechanism for the creation of thermostable D-AADH from U. thermosphaericus meso-DAPDH by point mutation.