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Information on EC 1.14.13.81 - magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclase and Organism(s) Hordeum vulgare and UniProt Accession Q5EFU4
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1.14.13.81 magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclaseIUBMB Comments
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 1.21.98.3, anaerobic magnesium-protoporphyrin IX monomethyl ester cyclase. Some facultative phototrophic bacteria, such as Rubrivivax gelatinosus, possess both enzymes.
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Word Map
- 1.14.13.81
- chlorophyll
- chloroplast
- protochlorophyllide
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isocyclic
- tetrapyrrole
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photosystems
- chelatase
- bacteriochlorophyll
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light-harvesting
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chlorotic
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pchlide
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diiron
- lhcii
- aureum
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rubrivivax
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anoxygenic
- gelatinosus
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epipremnum
- synthesis
The taxonomic range for the selected organisms is: Hordeum vulgare
The expected taxonomic range for this enzyme is: Bacteria, Eukaryota, Archaea
The expected taxonomic range for this enzyme is: Bacteria, Eukaryota, Archaea
Reaction Schemes
hide(Overall reactions are displayed. Show all >>)
Synonyms
chl27, mg-protoporphyrin ix monomethyl ester cyclase, xantha-l, pempec, sll1214, mg-protoporphyrin ix monomethyl ester (oxidative) cyclase, mg protoporphyrin monomethylester cyclase, oscrd1, mpe-cyclase, magnesium-protoporphyrin ix monomethyl ester cyclase, 
more
topSYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
cyclase, magnesium protoporphyrin IX monomethyl ester
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magnesium-protoporphyrin-IX monomethyl ester cyclase
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magnesium-protoporphyrin-IX monomethyl ester oxidative cyclase
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Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
magnesium-protoporphyrin IX 13-monomethyl ester + 3 NADPH + 3 H+ + 3 O2 = 3,8-divinyl protochlorophyllide a + 3 NADP+ + 5 H2O
overall reaction, reaction mechanism of the aerobic cyclase reaction, overview. The cyclase reaction is a six-electron redox reaction suggested to proceed via beta-hydroxy and beta-keto intermediates. The electrons are provided by Fd. NADPH can be used as the source of electrons transferred to ferredoxin (Fd) via ferredoxin-NADPH oxidoreductase (FNR). In green tissue, Fd can also be reduced by photosystem I
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
cyclization
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redox reaction
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oxidation
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reduction
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PATHWAY SOURCE
PATHWAYS
BRENDA
SYSTEMATIC NAME
IUBMB Comments
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 1.21.98.3, anaerobic magnesium-protoporphyrin IX monomethyl ester cyclase. Some facultative phototrophic bacteria, such as Rubrivivax gelatinosus, possess both enzymes.
CAS REGISTRY NUMBER
COMMENTARY
92353-62-3
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
magnesium-protoporphyrin IX 13-monomethyl ester + 3 NADPH + 3 H+ + 3 O2
3,8-divinyl protochlorophyllide a + 3 NADP+ + 5 H2O
overall reaction
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?
magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2
magnesium-protochlorophyllide + NADP+ + H2O
magnesium-protoporphyrin IX monomethyl ester + NADPH + H+ + O2
protochlorophyllide a + NADP+ + H2O
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intermediates are 6-beta-hydroxy analogue and 6-beta-oxo analogue of protochlorophyllide a
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131-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + O2
131-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + NADP+ + H2O
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131-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2
divinylprotochlorophyllide + NADP+ + 2 H2O
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magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2
131-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + NADP+ + H2O
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?
magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2
magnesium-protochlorophyllide + NADP+ + H2O
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ir
magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2
magnesium-protochlorophyllide + NADP+ + H2O
the enzyme is involved in the chlorophyll biosynthesis
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ir
additional information
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in vitro cyclase activity is obtained with recombinant XanL in combination with ferredoxin (Fd) and ferredoxin-NADPH oxidoreductase (FNR). Fd and FNR are plastid-localized redox components. Enzymatic assays combining spinach Fd and FNR with XanL[coYcf54] show high activity
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additional information
?
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in vitro cyclase activity is obtained with recombinant XanL in combination with ferredoxin (Fd) and ferredoxin-NADPH oxidoreductase (FNR). Fd and FNR are plastid-localized redox components. Enzymatic assays combining spinach Fd and FNR with XanL[coYcf54] show high activity
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additional information
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the enzyme is involved in the chlorophyll biosynthetic pathway, the chlorophyll biosynthetic intermediates Mg-protoporphyrin IX and Mg-protoporphyrin IX monomethyl ester are used as a signal molecules in the chloroplast-to-nucleus signal transduction for regulation of nucleus-located Lhc genes encoding chlorophyll a/b binding proteins of the light-harvesting complex
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NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
magnesium-protoporphyrin IX 13-monomethyl ester + 3 NADPH + 3 H+ + 3 O2
3,8-divinyl protochlorophyllide a + 3 NADP+ + 5 H2O
overall reaction
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-
?
magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2
magnesium-protochlorophyllide + NADP+ + H2O
the enzyme is involved in the chlorophyll biosynthesis
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ir
magnesium-protoporphyrin IX monomethyl ester + NADPH + H+ + O2
protochlorophyllide a + NADP+ + H2O
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intermediates are 6-beta-hydroxy analogue and 6-beta-oxo analogue of protochlorophyllide a
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?
131-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + O2
131-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + NADP+ + H2O
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?
131-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2
divinylprotochlorophyllide + NADP+ + 2 H2O
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?
magnesium-protoporphyrin IX 13-monomethyl ester + NADPH + H+ + O2
131-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + NADP+ + H2O
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?
additional information
?
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the enzyme is involved in the chlorophyll biosynthetic pathway, the chlorophyll biosynthetic intermediates Mg-protoporphyrin IX and Mg-protoporphyrin IX monomethyl ester are used as a signal molecules in the chloroplast-to-nucleus signal transduction for regulation of nucleus-located Lhc genes encoding chlorophyll a/b binding proteins of the light-harvesting complex
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Fe2+
required, the aerobic cyclase belongs to the family of diiron carboxylate-bridged proteins characterized by the iron-binding motif E-Xn-E-X-X-H-Xn-E-Xn-E-X-X-H
Mg2+
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
assays performed with barley extract are inhibited by antibodies raised against ferredoxin and ferredoxin-NADPH oxidoreductase (FNR)
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additional information
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assays performed with barley extract are inhibited by antibodies raised against ferredoxin and ferredoxin-NADPH oxidoreductase (FNR)
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
XanL
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required by the enzyme, found associated with the membrane and protein Ycf54
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Ycf54
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identified based upon strong association of Ycf54 with XanL. Active Ycf54 is membrane localized. The conserved chloroplast polypeptide Ycf54 is involved in the MPEC-enzyme catalyzed reaction. Sequencing, recombinant expression as His-tagged protein, and purification, UniProt ID F2D891
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
30
ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
gene xantha-I; cv. Bonus, the aerobic cyclase is composed of three gene products, a soluble protein, a membrane-bound component encoded by xantha-l, and another membrane-bound component encoded by viridis-k
SwissProt
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
additional information
in photosynthetic tissue, undetectable in non-photosynthetic tissues
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
the aerobic cyclase is composed of three gene products, a soluble protein, a membrane-bound component encoded by xantha-l, and another membrane-bound component encoded by viridis-k
the aerobic cyclase is composed of three gene products, a soluble protein, a membrane-bound component encoded by xantha-l, and another membrane-bound component encoded by viridis-k
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
evolution
two distinct enzymes have been identified that catalyze the cyclase reaction, originally distinguished by the source of the incorporated oxygen. The enzyme that catalyzes the cyclase reaction in the absence of molecular oxygen (anaerobic) derives the oxygen from water and is encoded by bchE in facultative photosynthetic bacteria like Rhodobacter sphaeroides. The anaerobic enzyme functions as a hydratase, whereas the aerobic cyclase is an oxygenase. The aerobic cyclase belongs to the family of diiron carboxylate-bridged proteins characterized by the iron-binding motif E-Xn-E-X-X-H-Xn-E-Xn-E-X-X-H. The cyclase activity requires both additional soluble and membrane-bound fractions
malfunction
xantha-l35 and viridis-k deficient mutants grown in the dark, fed with delta-aminolevulinic acid, accumulate the substrate magnesium-protoporphyrin IX monomethyl ester and produce reduced amounts of protochlorophyllide a, in vitro complementation assay with mutants the aerobic cyclase is composed of at least 3 gene products, 1 soluble and 2 membrane-bound proteins (xantha-l and viridian-k)
metabolism
physiological function
the Xantha-l gene product (XanL) is a membrane-bound diiron monooxygenase, which requires additional soluble and membrane-bound components for its activity. The enzyme XanL is a Mg-protoporphyrin IX monomethyl ester cyclase involved in the formation of the isocyclic E-ring characteristic of chlorophylls. The MPE cyclase is a ferredoxin-dependent enzyme. Ferredoxin is part of the photosynthetic electron-transport chain, which suggests that the cyclase reaction might be connected to photosynthesis under light conditions
malfunction
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Hordeum vulgare mutants viridis-k, light green 3, light green 4 and zebra stripe 2 are not deficient in Ycf54. Both xanthan-l and viridis-k membranes are unable to support MPEC activity when combined with wild-type soluble fraction
physiological function
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enzyme MPEC requires components found in both the membrane and soluble fractions of the chloroplast. It requires components associated with the plastid membrane and the plastid soluble fraction for activity. One of the components, XanL is found associated with the membrane and another protein, Ycf54 has been identified based upon its strong association of with XanL. The conserved chloroplast polypeptide Ycf54 is involved in the MPEC-enzyme catalyzed reaction
metabolism
protochlorophyllide a production (formation of the isocyclic ring) via several intermediates in the chlorophyll biosynthesis pathway
metabolism
in the first unique step of the chlorophyll biosynthetic pathway, Mg2+ is inserted into protoporphyrin IX. Subsequently, a methyl group is transferred to the carboxyl group of the propionate on the C ring of Mg-protoporphyrin IX, generating Mg-protoporphyrin IX monomethyl ester (MPE), which is the substrate of the MPE cyclase. The cyclase catalyzes the formation of the isocyclic E ring by insertion of oxygen and attaching the methylated propionate to the methene bridge between pyrrole rings C and D, forming protochlorophyllide. Chlorophyll is obtained after additional reactions involving a light-dependent oxidation of protochlorophyllide to chlorophyllide, reduction of the vinyl group on the B ring, and, finally, addition of a polyisoprene tail
UNIPROT
ENTRY NAME
ORGANISM
NO. OF AA
NO. OF TRANSM. HELICES
MOLECULAR WEIGHT[Da]
SOURCE
SEQUENCE
LOCALIZATION PREDICTION
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable).
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable). CRD1_HORVU
417
0
48161
Swiss-Prot
Chloroplast (Reliability: 2)
SUBUNIT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
heterodimer
highly conserved leucin zipper domain and EXnEXRH motif (binding binuclear-iron cluster)
additional information
additional information
the aerobic cyclase is composed of three different subunits: a soluble protein, a membrane-bound component encoded by Xantha-l, and another membrane-bound component encoded by viridis-k
additional information
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the aerobic cyclase is composed of three different subunits: a soluble protein, a membrane-bound component encoded by Xantha-l, and another membrane-bound component encoded by viridis-k
PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
additional information
additional information
construction of xantha-l35, xantha-l81, xantha-l82, viridis-k23, and viridis-k170 mutants, the mutants are all inactive in cyclase activity, phenotypes of mutant plants, overview
additional information
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construction of xantha-l35, xantha-l81, xantha-l82, viridis-k23, and viridis-k170 mutants, the mutants are all inactive in cyclase activity, phenotypes of mutant plants, overview
additional information
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identification of a xantha-l mutant, defective in a gene of Mg-protoporphyrin monomethyl ester cyclase, the mutant does not show the gun mutant phenotype, that is defective in the chloroplast-to-nucleus signal transduction and expresses Lhc even when chloroplast development is inhibited by the herbicide norflurazon, the xantha-181 mutant can synthesize Mg-protoporphyrin IX and Mg-protoporphyrin IX monomethyl ester, phenotype, overview
PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
partially by chloroplast supernatant and membrane preparation of wild-type and recombinant mutant plants
CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
gene xantha-1, DNA and amino acid sequence determination and analysis, expression of wild-type and mutants in transgenic barley plants
gene Xantha-I, recombinant expression of active XanL strictly requires co-expression with an additional protein, Ycf54, recombinant expression of His-tagegd XanL and Ycf54 in Escherichia coli strain Artic Express (DE3)
REF.
AUTHORS
TITLE
JOURNAL
VOL.
PAGES
YEAR
ORGANISM (UNIPROT)
PUBMED ID
SOURCE
Gadjieva, R.; Axelsson, E.; Olsson, U.; Hansson, M.
Analysis of gun phenotype in barley magnesium chelatase and Mg-protoporphyrin IX monomethyl ester cyclase mutants
Plant Physiol. Biochem.
43
901-908
2005
Hordeum vulgare
Rzeznicka, K.; Walker, C.J.; Westergren, T.; Kannangara, C.G.; von Wettstein, D.; Merchant, S.; Gough, S.P.; Hansson, M.
Xantha-l encodes a membrane subunit of the aerobic Mg-protoporphyrin IX monomethyl ester cyclase involved in chlorophyll biosynthesis
Proc. Natl. Acad. Sci. USA
102
5886-5891
2005
Hordeum vulgare (Q5EFU4), Hordeum vulgare
Liu, H.; Zheng, C.
MPEC: An important gene in the chlorophyll biosynthesis pathway in photosynthetic organisms
Photosynthetica
46
321-328
2008
Arabidopsis thaliana (Q9M591), Brassica napus (Q7XJI2), Chlamydomonas reinhardtii (Q9AR22), Chlamydomonas reinhardtii (Q9LD46), Cucumis sativus, Hordeum vulgare (Q5EFU4), Ipomoea nil (Q40093), Nicotiana tabacum, Oryza sativa, Rosa davurica, Rubrivivax gelatinosus (P0DJN9), Salix babylonica (Q7XJI4), Spinacia oleracea (Q7XJI5), Trifolium repens (Q7XJI1), Triticum aestivum (Q7XJI6)
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Bollivar, D.; Braumann, I.; Berendt, K.; Gough, S.P.; Hansson, M.
The Ycf54 protein is part of the membrane component of Mg-protoporphyrin IX monomethyl ester cyclase from barley (Hordeum vulgare L.)
FEBS J.
281
2377-2386
2014
Hordeum vulgare
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