EC - Cyclic pyranopterin monophosphate synthase

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IntEnz Enzyme Nomenclature


Accepted name:
cyclic pyranopterin monophosphate synthase
Other names:
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)



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

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0061799
UniProtKB/Swiss-Prot: (371) [show] [UniProt]


  1. Rieder, C., Eisenreich, W., O'Brien, J., Richter, G., Gotze, E., Boyle, P., Blanchard, S., Bacher, A., Simon, H.
    Rearrangement reactions in the biosynthesis of molybdopterin--an NMR study with multiply 13C/15N labelled precursors.
    Eur. J. Biochem. 255: 24-36 (1998). [PMID: 9692897]
  2. Wuebbens, M. M., 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: 1082-1087 (1995). [PMID: 7836363]
  3. Hover, B. M., Tonthat, N. K., Schumacher, M. A., Yokoyama, K.
    Mechanism of pyranopterin ring formation in molybdenum cofactor biosynthesis.
    Proc. Natl. Acad. Sci. U.S.A. 112: 6347-6352 (2015). [PMID: 25941396]

[EC created 2016]