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The high‐resolution X‐ray crystal structure of the ternary complex FtmOx1 ⋅ 2OG ⋅ fumitremorgin B and the catalytic mechanism were recently reported by us (DOI 10.1002/anie.202112063). In their Correspondence, Zhang, Costello, Liu et al. criticize our work in several aspects. Herein, we address these questions one by one. These structural clarifications and new computational results further support the CarC‐like mechanistic model. [ABSTRACT FROM AUTHOR]

The non‐heme iron ergothioneine synthase (EgtB) is a sulfoxide synthase that catalyzes oxidative C−S bond formation in the synthesis of ergothioneine, which plays roles against oxidative stress in cells. Despite extensive experimental and computational studies of the catalytic mechanisms of EgtB, the root causes for the selective C−S bond formation remain elusive. Using quantum mechanics/molecular mechanics (QM/MM) calculations, we show herein that a coordination switch of the sulfoxide intermediate is involved in the catalysis of the non‐heme iron EgtB. This coordination switch from the S to the O atom is driven by the S/π electrostatic interactions, which efficiently promotes the observed stereoselective C−S bond formation while bypassing cysteine dioxygenation. The present mechanism is in agreement with all available experimental data, including regioselectivity, stereoselectivity and KIE results. This match underscores the critical role of coordination switching in the catalysis of non‐heme enzymes. [ABSTRACT FROM AUTHOR]