IUBMB Enzyme Nomenclature


Accepted name: phosphomethylpyrimidine synthase

Reaction: 5-amino-1-(5-phospho-D-ribosyl)imidazole + S-adenosyl-L-methionine = 4-amino-2-methyl-5-(phosphooxymethyl)pyrimidine + 5'-deoxyadenosine + L-methionine + formate + CO

For diagram of reaction click here.

Other name(s): thiC (gene name)

Systematic name: 5-amino-1-(5-phospho-D-ribosyl)imidazole formate-lyase (decarboxylating, 4-amino-2-methyl-5-(phosphooxymethyl)pyrimidine-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 L-methionine and a 5'-deoxyadenosin-5'-yl radical that is crucial for the conversion of the substrate. Part of the pathway for thiamine biosynthesis.

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


1. Chatterjee, A., Li, Y., Zhang, Y., Grove, T.L., Lee, M., Krebs, C., Booker, S.J., Begley, T.P. and Ealick, S.E. Reconstitution of ThiC in thiamine pyrimidine biosynthesis expands the radical SAM superfamily. Nat. Chem. Biol. 4 (2008) 758-765. [PMID: 18953358]

2. Martinez-Gomez, N.C., Poyner, R.R., Mansoorabadi, S.O., Reed, G.H. and Downs, D.M. Reaction of AdoMet with ThiC generates a backbone free radical. Biochemistry 48 (2009) 217-219. [PMID: 19113839]

3. Chatterjee, A., Hazra, A.B., Abdelwahed, S., Hilmey, D.G. and Begley, T.P. A "radical dance" in thiamin biosynthesis: mechanistic analysis of the bacterial hydroxymethylpyrimidine phosphate synthase. Angew. Chem. Int. Ed. Engl. 49 (2010) 8653-8656. [PMID: 20886485]

[EC created 2011]

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