Conversion of a non-heme iron-dependent sulfoxide synthase into a thiol dioxygenase by a single point mutation

EgtB from Mycobacterium thermoresistibile catalyzes O2-dependent sulfur-carbon bond formation between the side chains of Nα-trimethyl histidine and γ-glutamyl cysteine as a central step in ergothioneine biosynthesis. A single point mutation converts this enzyme into a γ-glutamyl cysteine dioxygenase with an efficiency that rivals naturally evolved thiol dioxygenases.