EC - Magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclase

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IntEnz Enzyme Nomenclature


Accepted name:
magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclase
Other names:
Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase
Mg-protoporphyrin IX monomethyl ester oxidative cyclase
Systematic name:
magnesium-protoporphyrin-IX 13-monomethyl ester,NADPH:oxygen oxidoreductase (hydroxylating)




Requires Fe(II) for activity. The enzyme participates in the biosynthesis of chlorophyllide a in aerobic organisms. The same transformation is achieved in anaerobic organisms by EC, anaerobic magnesium-protoporphyrin IX monomethyl ester cyclase. Some facultative phototrophic bacteria, such as Rubrivivax gelatinosus, possess both enzymes.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0048529
CAS Registry Number: 92353-62-3
UniProtKB/Swiss-Prot: (45) [show] [UniProt]


  1. Walker, C. J., Mansfield, K. E., Rezzano, I. N., Hanamoto, C. M., Smith, K. M., Castelfranco, P. A.
    The magnesium-protoporphyrin IX (oxidative) cyclase system. Studies on the mechanism and specificity of the reaction sequence.
    Biochem. J. 255 : 685-692 (1988). [PMID: 3202840]
  2. Bollivar, D.W. and Beale, S.I.
    The chlorophyll biosynthetic enzyme Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase (characterization and partial purification from Chlamydomonas reinhardtii and Synechocystis sp. PCC 6803).
    Plant Physiol. 112 : 105-114 (1996). [PMID: 12226378]
  3. Pinta, V., Picaud, M., Reiss-Husson, F., Astier, C.
    Rubrivivax gelatinosus acsF (previously orf358) codes for a conserved, putative binuclear-iron-cluster-containing protein involved in aerobic oxidative cyclization of Mg-protoporphyrin IX monomethylester.
    J. Bacteriol. 184 : 746-753 (2002). [PMID: 11790744]
  4. Tottey, S., Block, M. A., Allen, M., Westergren, T., Albrieux, C., Scheller, H. V., Merchant, S., Jensen, P. E.
    Arabidopsis CHL27, located in both envelope and thylakoid membranes, is required for the synthesis of protochlorophyllide.
    Proc. Natl. Acad. Sci. U.S.A. 100 : 16119-16124 (2003). [PMID: 14673103]

[EC created 2003, modified 2017]