Reaction: magnesium-protoporphyrin IX 13-monomethyl ester + 3 NADPH + 3 H+ + 3 O2 = divinylprotochlorophyllide + 3 NADP+ + 5 H2O (overall reaction)
(1a) magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2 = 131-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + NADP+ + H2O
(1b) 131-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2 = 131-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + NADP+ + 2 H2O
(1c) 131-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2 = divinylprotochlorophyllide + NADP+ + 2 H2O
For diagram of reaction click here (chlorophyll biosynthesis).
Other name(s): Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase
Systematic name: magnesium-protoporphyrin-IX 13-monomethyl ester,NADPH:oxygen oxidoreductase (hydroxylating)
Comments: Requires Fe(II) for activity. The cyclase activity in Chlamydomonas reinhardtii is associated exclusively with the membranes, whereas that from cucumber cotyledons requires both membrane and soluble fractions for activity.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 92353-62-3
References:
1. 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 (1996) 105-114. [PMID: 12226378]