Information on EC 6.6.1.1 - magnesium chelatase

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The expected taxonomic range for this enzyme is: Eukaryota, Bacteria

EC NUMBER
COMMENTARY hide
6.6.1.1
-
RECOMMENDED NAME
GeneOntology No.
magnesium chelatase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
ATP + protoporphyrin IX + Mg2+ + H2O = ADP + phosphate + Mg-protoporphyrin IX + 2 H+
show the reaction diagram
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Ligation
-
-
-
-
PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
3,8-divinyl-chlorophyllide a biosynthesis I (aerobic, light-dependent)
-
-
3,8-divinyl-chlorophyllide a biosynthesis II (anaerobic)
-
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3,8-divinyl-chlorophyllide a biosynthesis III (aerobic, light independent)
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Biosynthesis of secondary metabolites
-
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chlorophyll metabolism
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Metabolic pathways
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Porphyrin and chlorophyll metabolism
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SYSTEMATIC NAME
IUBMB Comments
Mg-protoporphyrin IX magnesium-lyase
This is the first committed step of chlorophyll biosynthesis and is a branchpoint of two major routes in the tetrapyrrole pathway.
CAS REGISTRY NUMBER
COMMENTARY hide
9074-88-8
-
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
-
-
-
Manually annotated by BRENDA team
cultivar Hongdeng
UniProt
Manually annotated by BRENDA team
SG1001 strain
UniProt
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
malfunction
metabolism
physiological function
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
ATP + deuteroporphyrin + Mg2+ + H2O
ADP + phosphate + Mg-deuteroporphyrin + H+
show the reaction diagram
-
-
-
-
?
ATP + deuteroporphyrin IX + Mg2+ + H2O
ADP + phosphate + Mg-deuteroporphyrin IX + H+
show the reaction diagram
ATP + protoporphyrin IX + Mg2+ + H2O
ADP + phosphate + Mg-protoporphyrin IX + H+
show the reaction diagram
additional information
?
-
NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
ATP + deuteroporphyrin IX + Mg2+ + H2O
ADP + phosphate + Mg-deuteroporphyrin IX + H+
show the reaction diagram
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magnesium chelatase catalyzes the first committed step in chlorophyll biosynthesis
-
-
?
ATP + protoporphyrin IX + Mg2+ + H2O
ADP + phosphate + Mg-protoporphyrin IX + H+
show the reaction diagram
additional information
?
-
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
Mg2+
-
marked inhibition above 10 mM
N-ethylmaleimide
porphyrin
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at high ChlH concentrations, substrate inhibition is very noticeable
thiomerosal
thioredoxin
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ATPase activity of recombinant CHLI1 is fully inactivated by oxidation and easily recovered by thioredoxin-assisted reduction
Urea
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20% inhibition with 100 mM, 50% inhibition with 250 mM, 90% inhibition with 800 mM
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
5-aminolevulinic acid
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0.01 mM, increases activity
GENOMES UNCOUPLED 4
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GUN4 enhances measureable Mg-protoporphyrin IX in chloroplast extracts
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Gun4
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addition of Gun4 up to 0.0005 mM stimulates the wild type enzyme 2-3fold. Up to 0.001 mM Gun4 resurrects the inactive gun5 and cch mutant Mg-chelatase reactions to the level seen in the wild type with no Gun4 present, particularly in the case of mutant gun5
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GUN4 protein
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activates Mg-chelatase
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.026 - 0.8
ATP
0.00099 - 0.008
deuteroporphyrin
0.0032
deuteroporphyrin IX
-
-
1.3 - 2.3
Mg2+
0.0006 - 0.00283
protoporphyrin IX
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.0009 - 0.0067
ATP
0.0013 - 0.0188
deuteroporphyrin
0.013
deuteroporphyrin IX
Synechocystis sp.
-
-
0.0028 - 0.0083
Mg2+
0.0003 - 0.03
protoporphyrin IX
kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.0075
ATP
Thermosynechococcus elongatus
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pH 7.7, 45C
4
0.0028
Mg2+
Thermosynechococcus elongatus
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pH 7.7, 45C
6
Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.005
porphyrin
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pH 7.7, 45C. At high ChlH concentrations, substrate inhibition is very noticeable
IC50 VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.02
N-ethylmaleimide
Pisum sativum
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potent, IC50 of 0.02 mM
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
0.000002
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activity in chloroplast extracts
0.0000024
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pellet of broken fractionated chloroplasts
0.0000026
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supernatant of broken fractionated chloroplasts
0.00002
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broken unfractionated chloroplasts
0.0001
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intact chloroplasts
additional information
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3fold to 4fold higher values than in cucumber chloroplasts
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
20 - 22
28
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assay at
32
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assay at
34
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assay at
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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5-week-old
Manually annotated by BRENDA team
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the CHLH gene encoding the H subunit of Mg-chelatase is induced by continuous white, red, far-red or blue light with an initial peak after 24 h light. Mg-chelatase subunit genes CHLI and CHLD and the ferrochelatase genes FC1 and FC2 are not strongly regulated at the level of transcript abundance, but the Mg-chelatase regulator GUN4 has an expression profile almost identical to that observed for CHLH. Transcription of both CHLH and GUN4 is primarily under the control of phytochromes A and B and compromised in the phytochrome-signalling mutants fhy1 and fhy3
Manually annotated by BRENDA team
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
additional information
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multicomponent enzyme, requires at least two proteins, one membrane-associated and one soluble
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Manually annotated by BRENDA team
PDB
SCOP
CATH
ORGANISM
UNIPROT
Rhodobacter capsulatus (strain ATCC BAA-309 / NBRC 16581 / SB1003)
Rhodobacter capsulatus (strain ATCC BAA-309 / NBRC 16581 / SB1003)
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
43000
-
subunit I ChlI, SDS-PAGE
44000
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subunit I ChlI, SDS-PAGE
93000
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subunit D ChlD, SDS-PAGE
94000
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subunit D ChlD, SDS-PAGE
150000
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
dimer
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2 * 40000, BchI subunit
heterotrimer
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1 * 148000 + 1 * 39000 + 1 * 73000, subunits ChlH, ChlI and ChlD
octamer
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8 * 70000, D subunit, the molecular mass of the polymeric protein is approximately 550000 Da
trimer
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1 * 40000 (I-subunit) + 1 * 70000 (D-subunit) + 1 * 140000 (H-subunit)
additional information
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
multiple wavelength anomalous dispersion method
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subunit BchH, at 25 A resolution. The apo structure contains three major lobe-shaped domains connected at a single point with additional densities at the tip of two lobes termed the thumb and finger. The substrate-bound BchH complex BchH Proto shows a distinct conformational change in the thumb and finger subdomains. Prolonged proteolysis of native apo-BchH produces a stable C-terminal fragment of 45 kDa, and protoporphyrin protects the full-length polypeptide from degradation
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using electron microscopy and small-angle x-ray scattering the structure of ChlH subunit is investigated. ChlH is a large, 148-kDa protein of 1326 residues, forming a cage-like assembly comprising the majority of the structure, attached to a globular N-terminal domain of 16 kDa by a narrow linker region. This N-terminal domain is adjacent to a 5 nm-diameter opening in the structure that allows access to a cavity
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pH STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
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inactive below pH 6.0 and above pH 10.5
644267
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
55
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melting temperature
GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
26% loss of activity in chloroplasts subjected to hypotonic lysis and freeze-thaw cycles
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high concentrations of protoporphyrin, ATP and Mg2+ during gentle lysis, stabilise
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
cation exchange chromatography
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HisTrap Ni2+ crude FF chelating column chromatography, gel filtration
mutant enzymes are purified by Ni2+ affinity column chromatography
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Ni-NTA agarose column chromatography and glutathione Sepharose 4B bead chromatography
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recombinant enzyme
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using Ni-NTA chromatography
Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
BchD, BchI and BchH proteins are expressed in Escherichia coli from the respective cloned Rhodobacter capsulatus genes; expression of bchD gene in Escherichia coli
cloning and sequencing of xantha-f mutants (140000 Da subunit)
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expressed in Escherichia coli
expressed in Escherichia coli and Arabidopsis thaliana Col-0 after transformation with Agrobacterium tumefaciens
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expressed in Escherichia coli as a His-tagged fusion protein
expressed in Escherichia coli BL21 cells
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expression in Escherichia coli
expression in Escherichia coli; expression in Escherichia coli; expression in Escherichia coli
expression of bchD gene in Escherichia coli
expression of central CHLD region in yeast
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expression of mutant maize ChlI alleles in Nicotiana benthamiana results in the formation of chlorotic lesions within 4 d of inoculation. Transient expression provides a convenient, high-throughput, qualitative assay for functional variation in the CHLI protein
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mutant enzymes are expressed in Escherichia coli
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Rhodobacter capsulatus H-subunit produced in Escherichia coli
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
CHLH1 expression dramatically declines after 25 days after full bloom. The application of abscisic acid significantly decreases the expression of CHLH1 in fruits
down-regulation of CHLI confers abscisic acid insensitivity in stomatal response in Arabidopsis
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the relative expression of CHLH1 in dehydrated leaves is 1.3times higher than that in control leaves
up-regulation of CHLI1 results in abscisic acid hypersensitivity in seed germination
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
L348F
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named abar-2, altered abscisic acid-related phenotypes in seed germination and postgermination growth but not in stomatal movement
L690F
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missense mutation of CHLH responsible for the rtl1 phenotype with abscisic acid-insensitive stomatal movements
S183F
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named abar-3, altered abscisic acid-related phenotypes in seed germination and postgermination growth but not in stomatal movement
D207N
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altered restriction enzyme site, no measurable magnesium chelatase activity, ATPase activity not affected
E424
deletion mutant (3bp) named xantha-f.10, no magnesium chelatase activity
L111F
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altered restriction enzyme site, no measurable magnesium chelatase activity, ATPase activity not affected
M632R
missense mutation named xantha-f.26, leaky mutant with 8% to 10% of the chlorophyll content but 100% protein level of wild-type phenotype
R298K
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altered restriction enzyme site, no measurable magnesium chelatase activity, ATPase activity not affected
D207N
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BchI mutant forms a complex with wild-type BchD. Mutant shows 7.2% of wild-type ATPase activity. Mutant is deficient of magnesium chelatase activity
L111F
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BchI mutant forms a complex with wild-type BchD. Mutant shows 5.5% of wild-type ATPase activity. Mutant is deficient of magnesium chelatase activity
R289K
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BchI mutant forms a complex with wild-type BchD. Mutant shows 10.9% of wild-type ATPase activity. Mutant is deficient of magnesium chelatase activity
V113G
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BchI mutant forms a complex with wild-type BchD. Mutant shows 25% of wild-type ATPase activity. Mutant shows magnesium chelatase activity. Magnesium chelatase assays containing a mixture of mutant BchI V113G and wild-type BchI have the effect of stimulating the activity
A942V
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the (gun5) mutation abolishes activity of Mg-chelatase subunit H. Increasing the ChlH concentration up to 0.02 mM restores approximately 50% activity in the presence of the gun5 mutation. The addition of Gun4 restores Mg-chelatase activity of the gun5 mutant enzyme
E152Q
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mutation in the AAA+ domain of ChlD binds to ChlI. Mutant shows low activity but assembles into complexes much like wild-type. Mutant shows 25% of wild-type activity. kcat/K0.5 for Mg2+ is 30% of wild-type. kcat and Km for deuteroporphyrin are reduced to the same extent
K49A
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mutation in the AAA+ domain of ChlD binds to ChlI. Mutant shows no activity. Mutant forms detecable amount of ChlID complexes
P595L
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the (cch) mutation abolishes activity of Mg-chelatase subunit H. Increasing the ChlH concentration up to 0.02 mM fully restores activity in the presence of the cch mutation. The addition of Gun4 restores Mg-chelatase activity of the cch mutant enzyme
R208A
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mutation in the AAA+ domain of ChlD binds to ChlI. Mutant shows reduced binding affinity to ChlI.Mutant shows 50% of wild-type activity (least impaired mutant). Effect on substrate handling is modest compared to wild-type. Specifictiy constants for Mg2+ and porphyrin are 70% of wild-type
R289A
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mutation in the AAA+ domain of ChlD binds to ChlI. Mutant shows reduced binding affinity to ChlI. Mutant shows 13% of wild-type activity. Mutant does not show a cooperative response to MgATP2- and has much weaker specificity toward Mg2+ than wild-type. Mutant has a lower specificity toward free porphyrin than wild-type
additional information
APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
agriculture
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use of the CLCrV silencing vector to study gene function in cotton, via replacement of the CLCrV coat protein gene by up to 500 bp of DNA homologous to the magnesium chelatase subunit I gene ChlI. Temperature can have a major impact on the extent of geminivirus-induced gene silencing
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