Fig. 2
From: Toward more efficient ergothioneine production using the fungal ergothioneine biosynthetic pathway
The biosynthetic pathway of ergothioneine (ERG) and the domain prediction of Tregt1 and Tregt2. A Conserved domain predictions of Tregt1 (NCBI Reference Sequence: XP_006968620) and Tregt2 (NCBI Reference Sequence: XP_006968735) from T. reesei. B The biosynthetic pathway of ERG in Neurospora crassa (solid arrow) and Mycobacterium smegmatis (dashed arrow). The ERG biosynthesis in N. crassa requires only two main enzymes (Egt1 and Egt2) while in M. smegmatis, a gene cluster egtABCDE is responsible for ERG biosynthesis. Egt1 is a bifunctional enzyme that catalyzes the first two steps: the addition of three methyl groups in l-histidine to form hercynine, and the formation of C–S bond between l-cysteine (l-Cys) and hercynine to form hercynylcysteine sulfoxide. M. smegmatis sulfoxide synthase utilizes γ-glutamylcysteine (γGC) but not cysteine as sulfur donor. l-Met, l-methionine; SAM, S-adenosylmethionine; l-Cys, l-cysteine; l-Glu, l-glutamic acid