Information on EC 1.16.1.8 - [methionine synthase] reductase

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

EC NUMBER
COMMENTARY hide
1.16.1.8
-
RECOMMENDED NAME
GeneOntology No.
[methionine synthase] reductase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
2 [methionine synthase]-methylcob(I)alamin + 2 S-adenosylhomocysteine + NADP+ = 2 [methionine synthase]-cob(II)alamin + NADPH + H+ + 2 S-adenosyl-L-methionine
show the reaction diagram
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
methyl group transfer
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-
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SYSTEMATIC NAME
IUBMB Comments
[methionine synthase]-methylcob(I)alamin,S-adenosylhomocysteine:NADP+ oxidoreductase
In humans, the enzyme is a flavoprotein containing FAD and FMN. The substrate of the enzyme is the inactivated [Co(II)] form of EC 2.1.1.13, methionine synthase. Electrons are transferred from NADPH to FAD to FMN. Defects in this enzyme lead to hereditary hyperhomocysteinemia.
CAS REGISTRY NUMBER
COMMENTARY hide
207004-87-3
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
-
-
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Manually annotated by BRENDA team
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-
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
malfunction
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the c.56+781 A>C (rs326119) variant of intron-1 of MTRR significantly increases the risk of congenital heart disease in the Han Chinese population and is highly related to septation defects. The c.56+781 C allele profoundly decreases MTRR transcription. Phenotype, overview
metabolism
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the MTRR gene is involved in tumorigenesis by regulating DNA methylation through activation of methionine synthase
physiological function
additional information
-
genotyping for the A66G polymorphism and analysis of the association with cancer risk reveals that the G allele and GG variant genotypes are associated with a significantly increased cancer risk
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
2 [methionine synthase]-methylcob(I)alamin + 2 S-adenosylhomocysteine + NADP+
2 [methionine synthase]-cob(II)alamin + NADPH + H+ + 2 S-adenosyl-L-methionine
show the reaction diagram
[methionine synthase]-cob(II)alamin + NADH + S-adenosyl-L-methionine
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + NAD+
show the reaction diagram
-
-
-
-
?
[Methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
?
show the reaction diagram
[Methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
[Methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + NADP+
show the reaction diagram
[methionine synthase]-cob(II)alamin + NADPH + S-adenosylmethionine
[methionine synthase]-methylcob(I)alamin + NADPH + S-adenosylhomocysteine
show the reaction diagram
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in presence of methionine synthase reductase, holoenzyme formation from apomethionine synthase and methylcobalamin is significantly enhanced due to stabilization of apomethionine synthase. In addition to reductase activity, methionine synthase reductase serves as a special chaperone for methionine synthase. It also has reductase activity for the reaction of aquacobalamin to cob(II)alamin
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-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + 2,6-dichlorophenolindophenol
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
-
-
-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + 3-acetylpyridine adenine dinucleotide phosphate
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
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-
-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + doxorubicin
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
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-
-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + ferricyanide
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
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-
-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + menadione
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
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-
-
?
[methionine synthase]-methylcob(I)alamin + S-adenosylhomocysteine + NADP+
[methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
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
2 [methionine synthase]-methylcob(I)alamin + 2 S-adenosylhomocysteine + NADP+
2 [methionine synthase]-cob(II)alamin + NADPH + H+ + 2 S-adenosyl-L-methionine
show the reaction diagram
[Methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
?
show the reaction diagram
[methionine synthase]-methylcob(I)alamin + S-adenosylhomocysteine + NADP+
[methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
show the reaction diagram
additional information
?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
additional information
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NAD(H) is a poor cofactor
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INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
2',5'-ADP
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
reduced flavodoxin
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under anaerobic growth conditions, oxidized ferredoxin (flavodoxin):NADP+ oxidoreductase accepts a hydride from NADPH and transfers the electron to flavodoxin, generating primarily flavodoxin semiquinone. Under anaerobic conditions the decarboxylation of pyruvate is coupled to reduction of flavodoxin, forming the flavodoxin hydroquinone. These reduced forms of flavodoxin bind to inactive cob(II)alamin enzyme, leading to a conformational change that is coupled with dissociation of His759 and protonation of the His759-Asp757-Ser810 triad. Although NADPH oxidation ultimately produces 2 equivalent of flavodoxin semiquinone, only one electron is transferred to methionine synthase during reductive methylation
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.0023 - 0.0038
2,6-dichlorophenolindophenol
0.0177 - 0.018
3-acetylpyridine adenine dinucleotide phosphate
0.0286 - 0.0366
doxorubicin
0.663 - 0.774
ferricyanide
0.0177 - 0.018
menadione
0.00264 - 0.00289
NADPH
additional information
additional information
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.43
2,6-dichlorophenolindophenol
Homo sapiens
Q9UBK8
variant I22/S175
0.86
3-acetylpyridine adenine dinucleotide phosphate
Homo sapiens
Q9UBK8
variant I22/S175
1.61
doxorubicin
Homo sapiens
Q9UBK8
variant I22/S175
8.24
ferricyanide
Homo sapiens
Q9UBK8
variant I22/S175
1.61
menadione
Homo sapiens
Q9UBK8
variant I22/S175
3.92
NADPH
Homo sapiens
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pH 7.5, 25C
Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.0001 - 0.0014
2',5'-ADP
0.003 - 0.037
NADP+
additional information
additional information
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steady-state inhibition studies
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
1.56
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
22 - 25
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assay at
25
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assay at
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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in vivo quantitative real-time PCR analysis of MTRR mRNA in cardiac tissue samples from congenital heart disease patients, overview
Manually annotated by BRENDA team
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
-
-
-
Manually annotated by BRENDA team
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
77000
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gel filtration
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
monomer
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1 * 78000, SDS-PAGE
additional information
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
MSR NADP(H)/FAD domain complex, sitting drop vapor diffusion method, 4C, 10 mg/ml protein in 10 mM Tris/HCl, pH 8.0, 0.5 mM DTT, 1 mM EDTA, and 0.05% NaN3, reservoir solution comprising 0.1 M Tris/HCl, pH 7.5, 0.2 M KBr, and 15% PEG 4000, crystal soaking in saturated NADP+ solution, X-ray diffraction structure determination and analysis at 1.9 A resolution
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
after expression by baculovirus-infected insect cells. the flavin mononuleotide cofactor dissociates readily from enzyme upon dilution, hence it is important to keep the concentration high during purification
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recombinant enzyme
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recombinant GST-tagged full-length enzyme and flavin-binding domain by glutathione affinity and anion exchange chromatography, followed by ultrafiltration
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expression in Escherichia coli
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expression of full-length enzyme and flavin-binding domain as GST-tagged proteins
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gene MTRR, genotyping for the A66G polymorphism and analysis of the association with cancer risk, overview. The G allele and GG variant genotypes are associated with a significantly increased cancer risk
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MTRR genotyping, quantitative real-time PCR enzyme expression analysis
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
the c.56+781 A>C (rs326119) variant of intron-1 of MTRR significantly increases the risk of congenital heart disease in the Han Chinese population. The c.56+781 C allele profoundly decreases MTRR transcription
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
A66G
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naturally occuring mutation, the MTRR polymorphism leads to a lower affinity for substrate methionine synthase compared to the wild-type enzyme
I22M
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natural occuring polymorphism, no significant association with bone mineral density or serum osteocalcin level
S175L
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natural occuring polymorphism, no significant association with bone mineral density or serum osteocalcin level
S698A
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site-directed mutagenesis, the mutant shows reduced activity with cytochrome c3+ as substrate compared to the wild-type enzyme, the S698A mutant displays a 6fold reduction in kcat/Km for NADPH
W697F
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site-directed mutagenesis, the mutant shows enhanced catalysis, noted by increases in kcat and kcat/Km(NADPH) for steady-state cytochrome c3+ reduction and a 10fold increase in the rate constant associated with hydride transfer, W697F shows a 2.4fold increase in kcat and a 4.8fold increase in catalytic efficiency for NADPH. The mutant displays modest decreases in cytochrome c3+ reduction, a 30fold decrease in the rate of FAD reduction, accumulation of a FADH2-NADP+ charge-transfer complex, and dramatically suppressed rates of interflavin electron transfer
W697H
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site-directed mutagenesis, the mutant shows increased activity with cytochrome c3+ as substrate compared to the wild-type enzyme
W697S
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site-directed mutagenesis, the mutant shows reduced activity with cytochrome c3+ as substrate compared to the wild-type enzyme
W697Y
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site-directed mutagenesis, the mutant shows enhanced catalysis, noted by increases in kcat and kcat/Km(NADPH) for steady-state cytochrome c3+ reduction and a 10fold increase in the rate constant associated with hydride transfer. W697Y shows a 3.4fold increase in kcat and a 6.7fold increase in catalytic efficiency for NADPH. The mutant displays modest decreases in cytochrome c3+ reduction, a 3.5fold decrease in the rate of FAD reduction, accumulation of a FADH2-NADP+ charge-transfer complex, and dramatically suppressed rates of interflavin electron transfer
additional information
APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
diagnostics
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the MTRR A66G polymorphism is a potential biomarker for cancer risk
medicine