IUBMB Enzyme Nomenclature


Accepted name: hercynylcysteine S-oxide lyase

Reaction: S-(hercyn-2-yl)-L-cysteine S-oxide + reduced acceptor = ergothioneine + pyruvate + NH3 + acceptor (overall reaction)
(1a) S-(hercyn-2-yl)-L-cysteine S-oxide + H2O = 2-(hydroxysulfanyl)hercynine + pyruvate + NH3
(1b) 2-(hydroxysulfanyl)hercynine + reduced acceptor = ergothioneine + acceptor + H2O (spontaneous)

Glossary: 2-(hydroxysulfanyl)hercynine = Nα,Nα,Nα-trimethyl-2-(hydroxysulfanyl)-L-histidine = 2-sulfenohercynine
ergothioneine = Nα,Nα,Nα-trimethyl-2-sulfanylidene-2,3-dihydro-L-histidine

Other name(s): egtE (gene name)

Systematic name: S-(hercyn-2-yl)-L-cysteine ergothioneine-hydroxysulfanolate-lyase

Comments: Contains pyridoxal 5'-phosphate. The enzyme, characterized from the bacterium Mycobacterium smegmatis, cayalyses the last step in the pathway of ergothioneine biosynthesis. The enzyme forms a 2-(hydroxysulfanyl)hercynine intermediate, which is reduced to ergothioneine non-enzymically by a thiol. In vitro, DTT can serve this function.

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


1. Seebeck, F.P. In vitro reconstitution of mycobacterial ergothioneine biosynthesis. J. Am. Chem. Soc. 132 (2010) 6632-6633. [PMID: 20420449]

2. 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]

3. Song, H., Hu, W., Naowarojna, N., Her, A.S., Wang, S., Desai, R., Qin, L., Chen, X. and Liu, P. Mechanistic studies of a novel C-S lyase in ergothioneine biosynthesis: the involvement of a sulfenic acid intermediate. Sci Rep 5 (2015) 11870. [PMID: 26149121]

[EC created 2017]

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