Enhanced activity towards polyacrylates and poly(vinyl acetate) by site-directed mutagenesis of Humicola insolens cutinase

Previous studies on the hydrolysis of polyacrylates by cutinase have found that cutinase from Humicola insolens can fulfill the requirement for a thermostable cutinase in the treatment of stickies from papermaking, but it has poor hydrolysis ability. To further improve its ability to hydrolyze the polymers in papermaking, we analyzed the structure of cutinase from H. insolens, and constructed three mutants L66A, I169A, and L66A/I169A to reduce the steric hindrance of the substrate binding region. The hydrolysis results for poly(methyl acrylate), poly(ethyl acrylate), and poly(vinyl acetate) showed the catalytic ability of the mutant L66A/I169A most significantly improved. Using polymer macroporous resin composites as substrate, the released products of L66A/I169A were 1.3-4.4 times higher than that of the wild-type enzyme. When polymer suspensions were no longer being deposited, that is, when the turbidity decrease was less than 1%, the amount of L66A/I169A added was reduced by 19%-51% compared with that of the wild-type enzyme. These results indicated that the removal of the gatekeeper structure above the substrate binding region of H. insolens cutinase enhances its ability to hydrolyze polymers, and provided a basis for the application of cutinase in the practical treatment of stickies.