High-level soluble expression of human aldehyde dehydrogenase 2 in Escherichia coli achieved through lactose-mediated induction optimization.

Aldehyde dehydrogenase 2 (ALDH2) plays a critical role in ethanol metabolism by converting toxic acetaldehyde to acetate. To investigate its functional mechanisms and potential therapeutic applications for alcohol-related diseases, heterologous expression of ALDH2 is essential. However, ALDH2 often forms inclusion bodies when expressed in Escherichia coli. In this work, the solubility of ALDH2 was enhanced by systematic optimization of expression conditions using IPTG and lactose as respective inducers. Under optimized conditions, the media yield of ALDH2 induced by IPTG and lactose reached 44.5 ± 1.3 and 48.7 ± 1.2 μg/mL respectively, representing 7.1- and 7.8-fold improvements over unoptimized conditions. Enzymatic characterization revealed that purified ALDH2 exhibited optimal activity of 9.7 U/mL at 37 °C and pH 8.0. This research demonstrates that optimizing expression conditions is an effective strategy to enhance the solubility of recombinant enzymes, while providing a practical solution for other enzymes prone to inclusion body formation.