Semi-Rational Design of Diaminopimelate Dehydrogenase from Symbiobacterium thermophilum Improved Its Activity toward Hydroxypyruvate for D-serine Synthesis

D-serine plays an essential role in the field of medicine and cosmetics. Diaminopimelate dehydrogenase (DAPDH) is a kind oxidoreductase that can reduce keto acid into corresponding D-amino acid. Because its high stereoselectivity lack by-product production, DAPDH has become preferred enzyme for efficient one-step synthesis acids. However, types with reductive amination function reported so far are limited. Although from Symbiobacterium thermophilum (StDAPDH) demonstrates activity toward series macromolecular acids, hydroxypyruvate (HPPA) not been reported. In this study, we investigated available StDAPDH/H227V HPPA by measuring desired product D-serine. After homologous structure modeling docking analysis concerning substrate-binding pocket, four residues, D92, D122, M152, N253, active pocket were predicted catalyzing HPPA. Through single-point saturation mutation iterative mutation, mutant D92E/D122W/M152S was obtained 8.64-fold increase activity, exhibiting specific 0.19 U/mg kcat value 3.96 s−1 Using molecular dynamics simulation, it speculated might be related to change substrate size enhancement interactions between key residues.