Identification and functional characterization of NAD(P)(+)‐dependent meso‐diaminopimelate dehydrogenase from Numidum massiliense

meso‐Diaminopimelate dehydrogenase (meso‐DAPDH) catalyzes the reversible NADP(+)‐dependent oxidative deamination of meso‐2,6‐diaminopimelate (meso‐DAP) to produce l‐2‐amino‐6‐oxopimelate. Moreover, d‐amino acid dehydrogenase (d‐AADHs) derived from protein‐engineered meso‐DAPDH is useful for one‐step synthesis of d‐amino acids with high optical purity. Here, we report the identification and functional characterization of a novel NAD(P)(+)‐dependent meso‐DAPDH from Numidum massiliense (NmDAPDH). After the gene encoding the putative NmDAPDH was expressed in recombinant Escherichia coli cells, the enzyme was purified 4.0‐fold to homogeneity from the crude extract through five purification steps. Although the previously known meso‐DAPDHs use only NADP(+) as a coenzyme, NmDAPDH was able to use both NADP(+) and NAD(+) as coenzymes. When NADP(+) was used as a coenzyme, NmDAPDH exhibited an approximately 2 times higher k (cat)/K (m) value toward meso‐DAP than that of meso‐DAPDH from Symbiobacterium thermophilum (StDAPDH). NmDAPDH also catalyzed the reductive amination of corresponding 2‐oxo acids to produce acidic d‐amino acids such as d‐aspartate and d‐glutamate. The optimum pH and temperature for the oxidative deamination of meso‐DAP were about 10.5 and 75°C, respectively. Like StDAPDH, NmDAPDH exhibited high stability: it retained more than 75% of its activity after 30 min at 60°C (pH 7.2) or at pHs ranging from 5.5 to 13.0 (50°C). Alignment of the amino acid sequences of NmDAPDH and the known meso‐DAPDHs suggested NmDAPDH has a hexameric structure. Given its specificity for both NADP(+) and NAD(+), high stability, and a broad range of reductive amination activity toward 2‐oxo acids, NmDAPDH appears to offer advantages for engineering a more effective d‐AADH.