Cyclic pyranopterin monophosphate synthase

{{Infobox enzyme

| Name = Cyclic pyranopterin monophosphate synthase

| EC_number = 4.1.99.18

| CAS_number =

| GO_code =

| image =

| width =

| caption =

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Cyclic pyranopterin monophosphate synthase ({{EC number|4.1.99.18}}, MOCS1A, MoaA, MoaC, molybdenum cofactor biosynthesis protein 1) is an enzyme with systematic name GTP 8,9-lyase (cyclic pyranopterin monophosphate-forming).{{cite journal | vauthors = Rieder C, Eisenreich W, O'Brien J, Richter G, Götze E, Boyle P, Blanchard S, Bacher A, Simon H | title = Rearrangement reactions in the biosynthesis of molybdopterin--an NMR study with multiply 13C/15N labelled precursors | journal = European Journal of Biochemistry | volume = 255 | issue = 1 | pages = 24–36 | date = July 1998 | pmid = 9692897 | doi = 10.1046/j.1432-1327.1998.2550024.x | doi-access = }}{{cite journal | vauthors = Wuebbens MM, Rajagopalan KV | title = Investigation of the early steps of molybdopterin biosynthesis in Escherichia coli through the use of in vivo labeling studies | journal = The Journal of Biological Chemistry | volume = 270 | issue = 3 | pages = 1082–7 | date = January 1995 | pmid = 7836363 | doi = 10.1074/jbc.270.3.1082 | doi-access = free }}{{cite journal | vauthors = Hänzelmann P, Hernández HL, Menzel C, García-Serres R, Huynh BH, Johnson MK, Mendel RR, Schindelin H | title = Characterization of MOCS1A, an oxygen-sensitive iron-sulfur protein involved in human molybdenum cofactor biosynthesis | journal = The Journal of Biological Chemistry | volume = 279 | issue = 33 | pages = 34721–32 | date = August 2004 | pmid = 15180982 | doi = 10.1074/jbc.M313398200 | doi-access = free }}{{cite journal | vauthors = Hänzelmann P, Schindelin H | title = Crystal structure of the S-adenosylmethionine-dependent enzyme MoaA and its implications for molybdenum cofactor deficiency in humans | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 101 | issue = 35 | pages = 12870–5 | date = August 2004 | pmid = 15317939 | pmc = 516487 | doi = 10.1073/pnas.0404624101 | doi-access = free }}{{cite journal | vauthors = Sanishvili R, Beasley S, Skarina T, Glesne D, Joachimiak A, Edwards A, Savchenko A | title = The crystal structure of Escherichia coli MoaB suggests a probable role in molybdenum cofactor synthesis | journal = The Journal of Biological Chemistry | volume = 279 | issue = 40 | pages = 42139–46 | date = October 2004 | pmid = 15269205 | pmc = 3366512 | doi = 10.1074/jbc.M407694200 | doi-access = free }}{{cite journal | vauthors = Hänzelmann P, Schindelin H | title = Binding of 5'-GTP to the C-terminal FeS cluster of the radical S-adenosylmethionine enzyme MoaA provides insights into its mechanism | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 18 | pages = 6829–34 | date = May 2006 | pmid = 16632608 | pmc = 1458979 | doi = 10.1073/pnas.0510711103 | doi-access = free }}{{cite journal | vauthors = Lees NS, Hänzelmann P, Hernandez HL, Subramanian S, Schindelin H, Johnson MK, Hoffman BM | title = ENDOR spectroscopy shows that guanine N1 binds to [4Fe-4S] cluster II of the S-adenosylmethionine-dependent enzyme MoaA: mechanistic implications | journal = Journal of the American Chemical Society | volume = 131 | issue = 26 | pages = 9184–5 | date = July 2009 | pmid = 19566093 | pmc = 2757093 | doi = 10.1021/ja903978u }} This enzyme catalyses the following chemical reaction

: GTP $\backslash rightleftharpoons$ cyclic pyranopterin monophosphate + diphosphate

This enzyme catalyses an early step in the biosynthesis of molybdopterin.