IUBMB Enzyme Nomenclature


Accepted name: cyclic pyranopterin monophosphate synthase

Reaction: (8S)-3',8-cyclo-7,8-dihydroguanosine 5'-triphosphate = cyclic pyranopterin phosphate + diphosphate

For diagram of reaction click here.

Other name(s): MOCS1B (gene name); moaC (gene name); cnx3 (gene name)

Systematic name: (8S)-3',8-cyclo-7,8-dihydroguanosine 5'-triphosphate lyase (cyclic pyranopterin phosphate-forming)

Comments: The enzyme catalyses an early step in the biosynthesis of the molybdenum cofactor (MoCo). In bacteria and plants the reaction is catalysed by MoaC and Cnx3, respectively. In mammals the reaction is catalysed by the MOCS1B domain of the bifuctional MOCS1 protein, which also catalyses EC, GTP 3',8-cyclase.

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


1. Rieder, C., Eisenreich, W., O'Brien, J., Richter, G., Götze, E., Boyle, P., Blanchard, S., Bacher, A. and Simon, H. Rearrangement reactions in the biosynthesis of molybdopterin - an NMR study with multiply 13C/15N labelled precursors. Eur. J. Biochem. 255 (1998) 24-36. [PMID: 9692897]

2. Wuebbens, M.M. and Rajagopalan, K.V. Investigation of the early steps of molybdopterin biosynthesis in Escherichia coli through the use of in vivo labeling studies. J. Biol. Chem. 270 (1995) 1082-1087. [PMID: 7836363]

3. Hover, B.M., Tonthat, N.K., Schumacher, M.A. and Yokoyama, K. Mechanism of pyranopterin ring formation in molybdenum cofactor biosynthesis. Proc. Natl. Acad. Sci. USA 112 (2015) 6347-6352. [PMID: 25941396]

[EC created 2011 as EC, part transferred 2016 to EC]

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