IUBMB Enzyme Nomenclature


Accepted name: 2-iminoacetate synthase

Reaction: L-tyrosine + S-adenosyl-L-methionine + NADPH = 2-iminoacetate + 4-methylphenol + 5'-deoxyadenosine + L-methionine + NADP+ + H+

For diagram of reaction click here.

Glossary: 4-methylphenol = 4-cresol = p-cresol

Other name(s): thiH (gene name)

Systematic name: L-tyrosine 4-methylphenol-lyase (2-iminoacetate-forming)

Comments: Binds a [4Fe-4S] cluster that is coordinated by 3 cysteines and an exchangeable S-adenosyl-L-methionine molecule. The first stage of catalysis is reduction of the S-adenosyl-L-methionine to produce methionine and a 5-deoxyadenosin-5-yl radical that is crucial for the conversion of the substrate. The reductant is assumed to be NADPH, which is provided by a flavoprotein:NADPH oxidoreductase system [4]. Part of the pathway for thiamine biosynthesis.

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


1. Leonardi, R., Fairhurst, S.A., Kriek, M., Lowe, D.J. and Roach, P.L. Thiamine biosynthesis in Escherichia coli: isolation and initial characterisation of the ThiGH complex. FEBS Lett. 539 (2003) 95-99. [PMID: 12650933]

2. Kriek, M., Martins, F., Challand, M.R., Croft, A. and Roach, P.L. Thiamine biosynthesis in Escherichia coli: identification of the intermediate and by-product derived from tyrosine. Angew. Chem. Int. Ed. Engl. 46 (2007) 9223-9226. [PMID: 17969213]

3. Kriek, M., Martins, F., Leonardi, R., Fairhurst, S.A., Lowe, D.J. and Roach, P.L. Thiazole synthase from Escherichia coli: an investigation of the substrates and purified proteins required for activity in vitro. J. Biol. Chem. 282 (2007) 17413-17423. [PMID: 17403671]

4. Challand, M.R., Martins, F.T. and Roach, P.L. Catalytic activity of the anaerobic tyrosine lyase required for thiamine biosynthesis in Escherichia coli. J. Biol. Chem. 285 (2010) 5240-5248. [PMID: 19923213]

[EC created 2011, modified 2014]

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