Cosolvent-induced spontaneous refolding of lipase.

The overexpression of proteins in Escherichia coli often results in the formation of inclusion bodies, which are biologically inactive, especially for proteins with exposed hydrophobic surfaces. Solubilization of inclusion bodies (IBs) and subsequent refolding is essential for obtaining correctly folded and active protein. However, protein refolding involves multiple steps-namely isolation, solubilization, and refolding-which is a labor-intensive process. In this study, we developed a strategy for soluble production and protein refolding. A fusion tag was applied to Burkholderia ambifaria lipase YCJ01, enabling abundant soluble expression in E. coli. Despite this, the soluble protein exhibited only partial enzymatic activity, suggesting an unfolded state of soluble lipase YCJ01. Lipase activity increased significantly after incubation with cosolvents, reaching 1003 U/mL, 754 U/mL, and 501 U/mL in 25% (v/w) glycerol, 15% (v/w) DMSO, and 4M trimethylamine N-oxide (TMAO) solutions, respectively. Correctly folded and highly active lipase YCJ01 with a natural N-terminus was obtained. Moreover, the cosolvent-induced refolding mechanism was elucidated through molecular dynamics simulations. Glycerol and DMSO were found to aggregate around hydrophobic regions of lipase, directly stabilizing structure by displacing water molecules and weakening water-protein hydrogen (H) bonds within the hydration shell. Conversely, TMAO molecules indirectly influenced the lipase structure by strengthening water-water H bonds. KEY POINTS: • Cosolvents enhance lipase activity, with glycerol showing the highest improvement. • MD simulations show glycerol and DMSO directly interact with hydrophobic regions. • Glycerol and DMSO stabilize lipase directly, while TMAO enhances stability indirectly.