IUBMB Enzyme Nomenclature


Accepted name: thioglycine synthase

Reaction: ATP + sulfide + a [methyl-coenzyme M reductase]-glycine = ADP + phosphate + a [methyl-coenzyme M reductase]-thioglycine

Glossary: thioglycine = 2-aminoethanethioic O-acid

Other name(s): ycaO (gene name) (ambiguous)

Systematic name: [methyl-coenzyme M reductase]-glycine—sulfur ligase (thioglycine-forming)

Comments: Requires Mg2+. The enzyme is found in anaerobic methanogenic and methanotrophic archaea, where it modifies a glycine residue in EC, coenzyme-B sulfoethylthiotransferase (methyl-CoM reductase). Upon binding to its substrate, an external source of sulfide attacks the target amide bond generating a tetrahedral intermediate. The amide oxyanion attacks the γ-phosphate of ATP, releasing ADP and forming a phosphorylated thiolate intermediate that collapses to form thioglycine and phosphate. In most organisms activity requires a second protein (TfuA) , which may allosterically activate this enzyme or assist in the delivery of sulfide to the substrate.

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


1. Nayak, D.D., Mahanta, N., Mitchell, D.A. and Metcalf, W.W. Post-translational thioamidation of methyl-coenzyme M reductase, a key enzyme in methanogenic and methanotrophic Archaea. Elife 6 (2017) e29218 . [PMID: 28880150]

2. Mahanta, N., Liu, A., Dong, S., Nair, S.K. and Mitchell, D.A. Enzymatic reconstitution of ribosomal peptide backbone thioamidation. Proc. Natl. Acad. Sci. USA 115 (2018) 3030-3035. [PMID: 29507203]

3. Dong, S.H., Liu, A., Mahanta, N., Mitchell, D.A. and Nair, S.K. Mechanistic basis for ribosomal peptide backbone modifications. ACS Cent. Sci. 5 (2019) 842-851. [PMID: 31139720]

[EC created 2020]

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