All1750 of Anabaena PCC 7120 encodes a novel NAD⁺-dependent amine dehydrogenase having broad substrate range

Native amine dehydrogenases (AmDHs) are rare and typically have narrow substrate specificity and low processivity. Therefore, they are often modified using protein engineering for industrial and pharmaceutical applications. This study presents identification and characterization of a novel native amine dehydrogenase (AmDH) encoding WD40 protein (All1750) from Anabaena PCC 7120. Heterologous expression of all1750 in E. coli enhanced its tolerance to abiotic stressors such as drought, cadmium, and NaCl, as evidenced by increase in gene expression (2-10-fold), spot assay results (3-4-fold) and decreased ROS generation (0.2-1.8-fold). Molecular docking analysis showed that All1750 has broad substrate binding activity, indicating its catalytic potential in amine oxidation. All1750 exhibited the appreciable enzymatic activity with acetophenone (0.8-1.0-fold increase), followed by 4-fluorophenyl acetone and 4-fluoropropiophenone. The Km values for acetophenone and 4-fluorophenyl acetone were 4.2-12.1-fold higher, suggesting a greater affinity of All1750 for these low-cost substrates compared to the expensive 4-fluoropropiophenone. Recombinant All1750 showed optimal enzyme activity at pH 8.0 and maintained thermo-stability at 70 °C with a half-life of approximately 3 h. Our findings provide valuable insights into the industrial application of the All1750 protein. This native AmDH from Anabaena can effectively utilize diverse cost-effective substrates, making it a promising biocatalyst for chiral amine biosynthesis.