Fusion Expression of Human Acetaldehyde Dehydrogenase 2 with NusA

Aldehyde dehydrogenase 2 (ALDH2) was fused with NusA-tag to solubly express a recombinant protein with good activity in Escherichia coli. Primers were designed according to the gene sequence of Aldh2, and the restriction enzyme sites EcoRI and XhoI were inserted into the 5' end to amplify the Aldh2 gene fragment, which was then ligated into the pMD19-T-Simple vector and transformed into E. coli DH5α. After sequencing, the correct Aldh2 gene fragment was cloned into the expression vector pET44b(+) at the downstream of NusA-tag between EcoRI and XhoI and transformed into E. coli BL21(DE3). Protein expression was induced using isopropyl-β-D-thiogalactopyranoside (IPTG), and the resultant fusion protein had good solubility and mainly existed in the supernatant. The optimal expression conditions were found to be induction at 37 ℃ for 3 h with 0.25 mmol/L IPTG. The optimal reaction pH and temperature for the recombinant protein were 7.0 and 37 ℃, respectively. The metal ions Ca²⁺, K⁺, Na⁺, Mg²⁺ and Mn²⁺ could improve the enzyme activity, and Mg²⁺ had the most pronounced effect, increasing the activity to 1.64 U/mL. The wild-type ALDH2 was expressed as an inclusion body in E. coli with an activity of 1.43 U/mL. These results indicated that the fusion expression with NusA is a good method for the preparation of recombinant ALDH2 in E. coli.