Overexpression and biochemical characterization of a carboxyspermidine dehydrogenase from Agrobacterium fabrum str. C58 and its application to carboxyspermidine production

Abstract BACKGROUND Carboxyspermidine (C‐Spd) is a potentially valuable polyamine carboxylate compound and an excellent building block for spermidine synthesis, which is a critical polyamine with significant implications for human health and longevity. C‐Spd can also be used to prepare multivalent cationic lipids and modify nucleoside probes. Because of these positive effects on human health, C‐Spd is of considerable interest as a food additive and pharmaceutical target. RESULTS A putative gene afcasdh from Agrobacterium fabrum str. C58, encoding carboxyspermidine dehydrogenase with C‐Spd biosynthesis activity, was synthesized and transformed into Escherichia coli BL21 (DE3) for overexpression. The recombinant Af CASDH was purified and fully characterized. The optimum temperature and pH for the recombinant enzyme were 30 °C and 7.5, respectively. The coupled catalytic strategy of Af CASDH and various NADPH regeneration systems were developed to enhance the efficient production of C‐Spd compound. Finally, the maximum titer of C‐Spd production successfully achieved 1.82 mmol L −1 with a yield of 91% by optimizing the catalytic conditions. CONCLUSION A novel Af CASDH from A. fabrum str. C58 was characterized that could catalyze the formation of C‐Spd from putrescine and l ‐aspartate‐β‐semialdehyde (L‐Asa). A whole‐cell catalytic strategy coupled with NADPH regeneration was established successfully for C‐Spd biosynthesis for the first time. The coupled system indicated that Af CASDH might provide a feasible method for the industrial production of C‐Spd. © 2021 Society of Chemical Industry.