Enhanced Volatile Methylsiloxanes Degradation through Designed Enzyme Local Electric Field

Abstract

Widespread application of man-made chemicals volatile methylsiloxanes (VMS) has caused a variety of environmental and health issues. Enzymatic degradation of VMS can be a promising eco-friendly solution. Recent advances in the directed evolution of cytochrome P450_BM3 have shown significant potential for VMS degradation. However, the current catalytic efficiency remains insufficient for industrial application. Here, taking the LSilOx4 mutant-catalyzed degradation of hexamethyldisiloxane as an example, we decipher the enzymatic degradation mechanism with advanced multiscale simulations. The successful degradation of VMS involves three main processes, with the rate-determining step corresponding to hydrogen atom transfer in the enzyme-catalyzed C-H hydroxylation process, which holds an average energy barrier of 17.7 kcal·mol^-1. Our findings demonstrate that the progressive evolution of the internal electric field (IEF) aligns with the experimentally observed increase in activity from wild-type P450_BM3 to engineered variants (e.g. LSilOx4). This correlation is further evidenced by comparisons with results from oriented external electric field (EEF) calculations. Notably, the catalytic effect of the oriented EEFs is preferentially achieved through stronger stabilization of the transition state compared to the reactant. We anticipate that our insights will pave a way for the rational design of enzymes through the evolution of their internal electric field.