Directed evolution of enzymatic silicon-carbon bond cleavage in siloxanes
Nicholas S. Sarai, Tyler J. Fulton, Ryen L. O’Meara, Kadina E. Johnston, Sabine Brinkmann‐Chen, Ryan R. Maar, Ron E. Tecklenburg, John M. Roberts, Jordan C. T. Reddel, Dimitris E. Katsoulis, Frances H. Arnold
Abstract
Volatile methylsiloxanes (VMS) are man-made, nonbiodegradable chemicals produced at a megaton-per-year scale, which leads to concern over their potential for environmental persistence, long-range transport, and bioaccumulation. We used directed evolution to engineer a variant of bacterial cytochrome P450 BM3 to break silicon-carbon bonds in linear and cyclic VMS. To accomplish silicon-carbon bond cleavage, the enzyme catalyzes two tandem oxidations of a siloxane methyl group, which is followed by putative [1,2]-Brook rearrangement and hydrolysis. Discovery of this so-called siloxane oxidase opens possibilities for the eventual biodegradation of VMS.