part of oxidoreductase activity, acting on X-H and Y-H to form an X-Y bond, with oxygen as acceptor ergothioneine biosynthetic process hercynylcysteine sulfoxide synthase activity https://github.com/geneontology/go-ontology/issues/11163 https://github.com/geneontology/go-ontology/issues/24051 https://github.com/geneontology/go-ontology/issues/30193 EC:1.21.3.10 dph RHEA:42704 2015-03-06T15:08:51Z GO:0061686 hercynylcysteine S-oxide synthase molecular_function hercynylcysteine sulfoxide synthase Catalysis of the reaction: L-cysteine + N-alpha,N-alpha,N-alpha-trimethyl-L-histidine (hercynine) + O2 = hercynylcysteine sulfoxide + H2O.