The nonheme iron EgtB and OvoA are sulfoxide synthases that catalyze oxidative C−S bond formation in the synthesis of ergothioneine and ovothiol. Despite the extensively experimental and computational studies of the catalytic mecha-nisms of these enzymes, the root causes for the selective C−S bond formation remains elusive. Using combined molecu-lar dynamics (MD) simulations and quantum mechanics/molecular mechanics (QM/MM) method, we show here that coordination dynamics of the sulfoxide intermediate is involved in the catalysis of nonheme iron EgtB. Such coordina-tion switch from S to O atom is driven by the S/ electrostatic interactions, which promotes efficiently the observed stereoselective C-S bond formation while bypassing cysteine dioxygenation. As such, the present mechanism high-lights the critical role of coordination dynamics in catalysis, and it is in agreement with all available experimental data, including regioselectivity, stereoselectivity and KIE results.
Supporting Information Origins of the Selective C−S Bond Formation by the Non-Heme Iron EgtB