LAUSR

With the advantages of biocatalytic method, enzymes have been excavated for the synthesis of chiral amino acids by the reductive amination of ketones, offering a promising way of producing pharmaceutical intermediates. In this work, a robust phenylalanine dehydrogenase (PheDH) with wide substrate spectrum and high catalytic efficiency was constructed through rational design and active-site-targeted site-specific mutagenesis by using the parent enzyme from Bacillus halodurans. Active sites with bonding substrate and surrounding the substrate binding pocket, 49L-50G-51G, 74M,77K, 122G-123T-124D-125M, 275N, 305L and 308V of the PheDH were identified. Noticeably, the new mutant PheDH (E113D-N276L) showed approximately 6.06-fold increment of kcat/Km in the oxidative deamination and more than 1.58-fold in the reductive amination compared to that of the wide type. Meanwhile, the PheDHs exhibit high capacity of accepting benzylic and aliphatic ketone substrates. The broad specificity, high catalytic efficiency and selectivity, and excellent thermal stability render these broad-spectrum enzymes an ideal target for further development toward a diagnostic reagent and pharmaceutical compounds application.