IUBMB Enzyme Nomenclature


Accepted name: hercynylcysteine S-oxide synthase

Reaction: hercynine + L-cysteine + O2 = S-(hercyn-2-yl)-L-cysteine S-oxide + H2O

For diagram of reaction click here

Glossary: hercynine = Nα,Nα,Nα-trimethyl-L-histidine

Other name(s): Egt1; Egt-1

Systematic name: hercynine,L-cysteine:oxygen [S-(hercyn-2-yl)-L-cysteine S-oxide-forming]

Comments: Requires Fe2+ for activity. The enzyme, found in fungal species, is part of a fusion protein that also has the the activity of EC, L-histidine Nα-methyltransferase. It is part of the biosynthesis pathway of ergothioneine. The enzyme can also use L-selenocysteine to produce hercynylselenocysteine, which can be converted to selenoneine.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Pluskal, T., Ueno, M. and Yanagida, M. Genetic and metabolomic dissection of the ergothioneine and selenoneine biosynthetic pathway in the fission yeast, S. pombe, and construction of an overproduction system. PLoS One 9 (2014) e97774. [PMID: 24828577]

[EC created 2015 as, transferred 2022 to EC]

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