Table 1. Ergothioneine Production by Recombinant MES in E. coli^a.

entry	enzymes	strain	+MoO42–	+WO42–	no metal
1	-	E. coli (Δmtn)	<20 nM	<20 nM	<20 nM
2	CaMES	E. coli (Δmtn)	370 ± 31 μM	411 ± 146 μM	420 ± 72 μM
3	CaMES	E. coli BL21	22 ± 2 μM	n.a.	23 ± 3 μM
4	AbMES	E. coli (Δmtn)	0.4 ± 0.3 μM	0.4 ± 0.2 μM	0.4 μM
5	EaMES	E. coli (Δmtn)	10 ± 8 μM	27 ± 22 μM	0.6 μM
6	hvMES	E. coli (Δmtn)	85 ± 5 μM	83 ± 3 μM	153 μM

^aCells were grown in CD medium in the presence of 1 mM TMH, 0.1 mM IPTG, and 10 μM Mo or W for 20 h at 25 °C. Cell-free lysates were cleared by centrifugation. Ergothioneine content was estimated based on an external standard (see the Supporting Information).