phosphomethylpyrimidine synthase

{{Infobox enzyme

| Name = Phosphomethylpyrimidine synthase

| EC_number = 4.1.99.17

| CAS_number =

| GO_code =

| image = 4s27.jpg

| width = 270

| caption = Phosphomethylpyrimidine synthase dimer, Arabidopsis thaliana

}}

Phosphomethylpyrimidine synthase ({{EnzExplorer|4.1.99.17}}, thiC (gene)) is an enzyme with systematic name 5-amino-1-(5-phospho-D-ribosyl)imidazole formate-lyase (decarboxylating, 4-amino-2-methyl-5-phosphomethylpyrimidine-forming).{{cite journal | vauthors = Chatterjee A, Li Y, Zhang Y, Grove TL, Lee M, Krebs C, Booker SJ, Begley TP, Ealick SE | title = Reconstitution of ThiC in thiamine pyrimidine biosynthesis expands the radical SAM superfamily | journal = Nature Chemical Biology | volume = 4 | issue = 12 | pages = 758–65 | date = December 2008 | pmid = 18953358 | pmc = 2587053 | doi = 10.1038/nchembio.121 }}{{cite journal | vauthors = Martinez-Gomez NC, Poyner RR, Mansoorabadi SO, Reed GH, Downs DM | title = Reaction of AdoMet with ThiC generates a backbone free radical | journal = Biochemistry | volume = 48 | issue = 2 | pages = 217–9 | date = January 2009 | pmid = 19113839 | pmc = 2654281 | doi = 10.1021/bi802154j }}{{cite journal | vauthors = Chatterjee A, Hazra AB, Abdelwahed S, Hilmey DG, Begley TP | title = A "radical dance" in thiamin biosynthesis: mechanistic analysis of the bacterial hydroxymethylpyrimidine phosphate synthase | journal = Angewandte Chemie | volume = 49 | issue = 46 | pages = 8653–6 | date = November 2010 | pmid = 20886485 | pmc = 3147014 | doi = 10.1002/anie.201003419 }} This enzyme catalyses the following chemical reaction

: 5-amino-1-(5-phospho-D-ribosyl)imidazole + S-adenosyl-L-methionine $\backslash rightleftharpoons$ 4-amino-2-methyl-5-phosphomethylpyrimidine + 5′-deoxyadenosine + L-methionine + formate + CO

This enzyme binds a 4Fe-4S cluster.

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The starting material is 5-aminoimidazole ribotide, which undergoes a rearrangement reaction via radical intermediates which incorporate the blue, green and red fragments shown into the product.{{cite journal |doi=10.1039/b207131m |title=Cofactor biosynthesis: An organic chemist's treasure trove |year=2006 |last1=Begley |first1=Tadhg P. |journal=Natural Product Reports |volume=23 |issue=1 |pages=15–18 |pmid=16453030 }}