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
1.16.1.8
-
RECOMMENDED NAME
GeneOntology No.
[methionine synthase] reductase
REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
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
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, causing 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
-
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 ACCESSION NO.
COMMENTARY
LITERATURE
methyl group transfer
-
-
-
-
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.
SYNONYMS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
EC 2.1.1.135
-
-
formerly
-
Methionine synthase cob(II)alamin reductase (methylating)
-
-
-
-
Methionine synthase reductase
-
-
-
-
Methionine synthase reductase
-
-
MSR
-
-
-
-
NADPH-dependent diflavin oxidoreductase
-
-
Reductase, methionine synthase
-
-
-
-
CAS REGISTRY NUMBER
COMMENTARY
207004-87-3
-
ORGANISM
COMMENTARY
LITERATURE
SEQUENCE CODE
SEQUENCE DB
SOURCE
expression by baculovirus-infected insect cells
-
-
Manually annotated by BRENDA team
patients with homocystinuria
Uniprot
Manually annotated by BRENDA team
postmenopausal women, certain genetic polymorphisms of enzyme leading to a reduced activity may cause hyperhomocysteinemia and affect bone metabolism
-
-
Manually annotated by BRENDA team
variant I22/L175; variant M22/S175
-
-
Manually annotated by BRENDA team
variant I22/S175; variant M22/S175
Uniprot
Manually annotated by BRENDA team
variant I22M
-
-
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
metabolism
-
the MTRR gene is involved in tumorigenesis by regulating DNA methylation through activation of methionine synthase
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 ACCESSION NO.
COMMENTARY
(Substrate)
LITERATURE
(Substrate)
COMMENTARY
(Product)
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
[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
[Methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + NADP+
show the reaction diagram
Q9UBK8
-
-
-
[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-adenosyl-L-methionine
?
show the reaction diagram
-
the enzyme is involved in reductive activation of methionine synthase:
-
-
-
[Methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
?
show the reaction diagram
Q9UBK8
the enzyme is involved in reductive activation of methionine synthase:, patients of the cblE complementation group of disorders of folate/cobalamin metabolism who are defective in reductive activation of methionine synthase exhibit megablastic anemia, developmental delay, hyperhomocysteinemia, and hypomethioninemia
-
-
-
[methionine synthase]-cob(II)alamin + NADPH + S-adenosylmethionine
[methionine synthase]-methylcob(I)alamin + NADPH + S-adenosylhomocysteine
show the reaction diagram
-
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
-
-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + 2,6-dichlorophenolindophenol
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
Q9UBK8
-
-
-
?
[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
Q9UBK8
-
-
-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + doxorubicin
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
Q9UBK8
-
-
-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + ferricyanide
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
Q9UBK8
-
-
-
?
[methionine synthase]-cob(II)alamin + S-adenosyl-L-methionine + menadione
[methionine synthase]methylcob(I)alamin + S-adenosylhomocysteine + ?
show the reaction diagram
Q9UBK8
-
-
-
?
[methionine synthase]-methylcob(I)alamin + S-adenosylhomocysteine + NADP+
[methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
show the reaction diagram
-
-
-
-
r
[methionine synthase]-methylcob(I)alamin + S-adenosylhomocysteine + NADP+
[methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
show the reaction diagram
-
MSR is a NADPH-dependent diflavin oxidoreductase required for the reductive regeneration of catalytically inert cob(II)alamin to cob(I)alamin, complex formation between the substrate's activation domain and MSR, and the substrate's activation domain and the isolated FMN-binding domain of MSR. Weshow that the MS activation domain interacts directly with the FMN-binding domain of MSR, overview, interaction of the enzyme with the substrate enzyme methionine synthase via the C-terminal domain involves the residues K987 and K1071, interaction with substrate mutants K987T and K1071T is affected, structure-function relationship, overview
-
-
r
[methionine synthase]-methylcob(I)alamin + S-adenosylhomocysteine + NADP+
[methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
show the reaction diagram
-
MSR is a flavoprotein that regenerates the active form of cobalamin-dependent methionine synthase
-
-
r
additional information
?
-
Q9UBK8
difference in the relative efficiency of the very common polymorphic variant of the enzyme, I22M, suggests a molecular mechanism underlying the risk associated wiith the M22 allele for mild hyperhomocysteinemia
-
-
-
additional information
?
-
-
biological implications of an attenuated mechanism of MS reactivation by MSR on methionine and folate metabolism, overview, the enzyme catalyzes also the inhibition of reduction of cytochrome c3+
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-
-
NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
(Substrate)
LITERATURE
(Substrate)
COMMENTARY
(Product)
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
[Methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
?
show the reaction diagram
-
the enzyme is involved in reductive activation of methionine synthase:
-
-
-
[Methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
?
show the reaction diagram
Q9UBK8
the enzyme is involved in reductive activation of methionine synthase:, patients of the cblE complementation group of disorders of folate/cobalamin metabolism who are defective in reductive activation of methionine synthase exhibit megablastic anemia, developmental delay, hyperhomocysteinemia, and hypomethioninemia
-
-
-
[methionine synthase]-methylcob(I)alamin + S-adenosylhomocysteine + NADP+
[methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
show the reaction diagram
-
-
-
-
r
[methionine synthase]-methylcob(I)alamin + S-adenosylhomocysteine + NADP+
[methionine synthase]-cob(II)alamin + NADPH + S-adenosyl-L-methionine
show the reaction diagram
-
MSR is a NADPH-dependent diflavin oxidoreductase required for the reductive regeneration of catalytically inert cob(II)alamin to cob(I)alamin, complex formation between the substrate's activation domain and MSR, and the substrate's activation domain and the isolated FMN-binding domain of MSR. Weshow that the MS activation domain interacts directly with the FMN-binding domain of MSR, overview
-
-
r
additional information
?
-
Q9UBK8
difference in the relative efficiency of the very common polymorphic variant of the enzyme, I22M, suggests a molecular mechanism underlying the risk associated wiith the M22 allele for mild hyperhomocysteinemia
-
-
-
additional information
?
-
-
biological implications of an attenuated mechanism of MS reactivation by MSR on methionine and folate metabolism, overview
-
-
-
COFACTOR
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
FAD
-
contains both FAD and FMN. The values of the midpoint potentials are -236 mV FAD oxidized/semiquinone and -264 mV FAD semiquinone/hydroquinone, variant M22/S175; contains both FAD and FMN. The values of the midpoint potentials are -252 mV FAD oxidized/semiquinone and -285 mV FAD semiquinone/hydroquinone, variant I22/L175
FAD
-
dual flavoprotein with an equimolar concentration of FAD, 0.9 mol per mol of enzyme, and FMN, 1.1 mol per mol of enzyme
FAD
-
MSR contains one FAD and one FMN cofactor per polypeptide and functions in the sequential transfer of reducing equivalents from NADPH to MS via its flavin centers
FAD
-
midpoint reduction potential
FMN
-
contains both FAD and FMN. The values of the midpoint potentials are -103 mV FMN oxidized/semiquinone and -175 mV FMN semiquinone/hydroquinone, variant I22/L175; contains both FAD and FMN. The values of the midpoint potentials are -114 mV FMN oxidized/semiquinone and -212 mV FMN semiquinone/hydroquinone, variant M22/S175
FMN
-
dual flavoprotein with an equimolar concentration of FAD, 0.9 mol per mol of enzyme, and FMN, 1.1 mol per mol of enzyme
FMN
-
MSR contains one FAD and one FMN cofactor per polypeptide and functions in the sequential transfer of reducing equivalents from NADPH to MS via its flavin centers
NADH
-
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
NADH
-
can replace NADPH but only at significantly higher and nonphysiological concentrations
NADP+
-
dependent on, binding structure, overview, the NADP+-bound FNR-like module of MSR spans the NADP(H)-binding domain, the FAD-binding domain, the connecting domain, and part of the extended hinge region
NADPH
-
preferred electron donor
NADPH
-
dependent on, binding structure, overview, the NADP+-bound FNR-like module of MSR spans the NADP(H)-binding domain, the FAD-binding domain, the connecting domain, and part of the extended hinge region
FMN
-
midpoint reduction potential
additional information
-
NAD(H) is a poor cofactor
-
INHIBITORS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
2',5'-ADP
-
inhibition of MSR-catalyzed reduction of cytochrome c3+
NADP+
-
inhibition of MSR-catalyzed reduction of cytochrome c3+
ACTIVATING COMPOUND
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
reduced flavodoxin
-
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]
KM VALUE [mM] Maximum
SUBSTRATE
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
0.0023
-
2,6-dichlorophenolindophenol
Q9UBK8
variant I22/S175
0.0038
-
2,6-dichlorophenolindophenol
Q9UBK8
variant I22/S175
0.0177
-
3-acetylpyridine adenine dinucleotide phosphate
Q9UBK8
variant I22/S175
0.018
-
3-acetylpyridine adenine dinucleotide phosphate
Q9UBK8
variant I22/S175
0.0286
-
Doxorubicin
Q9UBK8
variant I22/S175
0.0366
-
Doxorubicin
Q9UBK8
variant I22/S175
0.663
-
ferricyanide
Q9UBK8
variant I22/S175
0.774
-
ferricyanide
Q9UBK8
variant I22/S175
0.0177
-
menadione
Q9UBK8
variant I22/S175
0.00264
-
NADPH
-
-
0.00289
-
NADPH
-
pH 7.5, 25C
0.018
-
menadione
Q9UBK8
variant I22/S175
additional information
-
additional information
-
isothermal titration calorimetry reveals a binding constant of 0.037 and 0.002 mM for binding of NADP+ and 2',5'-ADP, respectively, for the ligand-protein complex formed with full-length MSR or the isolated FNR module
-
additional information
-
additional information
-
lack of control on the thermodynamics and kinetics of electron transfer in MSR, overview
-
TURNOVER NUMBER [1/s]
TURNOVER NUMBER MAXIMUM[1/s]
SUBSTRATE
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
0.43
-
2,6-dichlorophenolindophenol
Q9UBK8
variant I22/S175
0.86
-
3-acetylpyridine adenine dinucleotide phosphate
Q9UBK8
variant I22/S175
1.61
-
Doxorubicin
Q9UBK8
variant I22/S175
8.24
-
ferricyanide
Q9UBK8
variant I22/S175
1.61
-
menadione
Q9UBK8
variant I22/S175
3.92
-
NADPH
-
pH 7.5, 25C
Ki VALUE [mM]
Ki VALUE [mM] Maximum
INHIBITOR
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
0.036
-
NADP+
-
inhibition of reduction of cytochrome c3+
0.0014
-
2',5'-ADP
-
inhibition of reduction of cytochrome c3+
additional information
-
additional information
-
steady-state inhibition studies
-
SPECIFIC ACTIVITY [µmol/min/mg]
SPECIFIC ACTIVITY MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
1.56
-
-
-
pH OPTIMUM
pH MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
7.5
-
-
assay at
TEMPERATURE OPTIMUM
TEMPERATURE OPTIMUM MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
25
-
-
assay at
LOCALIZATION
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
MOLECULAR WEIGHT
MOLECULAR WEIGHT MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
77000
-
-
gel filtration
SUBUNITS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
?
Q9UBK8
x * 77000, calculation from nucleotide sequence
?
-
x * 78000, SDS-PAGE
monomer
-
1 * 78000, SDS-PAGE
additional information
-
in addition to reductase activity, methionine synthase reductase serves as a special chaperone for methionine synthase
additional information
-
the NADP+-bound FNR-like module of MSR spans the NADP(H)-binding domain, the FAD-binding domain, the connecting domain, and part of the extended hinge region
additional information
-
the inferred multidomain structure of MSR and the presence of a large linker between the component flavin-containing domains suggest a large degree of conformational flexibility in the protein. MSR fluctuates between closed and open conformations, modeling, overview. Analysis of the complex structure formed between MSR, NADP+ and MS activation domain using the crystal structure, PDB ID 2QTZ, 2O2K, and 3ES9, overview
Crystallization/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
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
-
Purification/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
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
-
recombinant enzyme
-
recombinant GST-tagged full-length enzyme and flavin-binding domain by glutathione affinity and anion exchange chromatography, followed by ultrafiltration
-
Cloned/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
-
Q9UBK8
expression in Escherichia coli
-
expression of full-length enzyme and flavin-binding domain as GST-tagged proteins
-
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
-
ENGINEERING
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
A66G
-
naturally occuring mutation, the MTRR polymorphism leads to a lower affinity for substrate methionine synthase compared to the wild-type enzyme
I22M
-
natural occuring polymorphism, no significant association with bone mineral density or serum osteocalcin level
S175L
-
natural occuring polymorphism, no significant association with bone mineral density or serum osteocalcin level
additional information
-
construction of mouse model with a gene trap in the methionine synthase reductase gene. Mutant animals have increased plasma homocyst(e)ine, decreased plasma methionine, and increased tissue methyltetrahydrofolate levels. Mice do not show decreases in the S-adenosylmethionine/S-adenosylhomocysteine ratio in most tissues
APPLICATION
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
diagnostics
-
the MTRR A66G polymorphism is a potential biomarker for cancer risk
medicine
Q9UBK8
cloning of the cDNA will permit the diagnostic characterization of cblE patients and investigation of the potential role of polymorphisms of this enzyme as a risk factor in hyperhomocysteinemia-linked vascular disease
medicine
-
variant M22/S175 is a genetic determinant of plasma homocysteine levels and has been linked to premature coronary artery disease, Downs syndrome, and neural tube defects
medicine
-
the common variant I22M in methionine synthase reductase combined with low vitamin B12 increases risk for spina bifida
medicine
-
study on association of natural polymorphisms I22M (A66G) and S175L (C524T) with bone mineral density and serum osteocalcin levels. No significant association between these two polymorphisms and bone mineral density and serum osteocalcin levels, but the 66G/524C haplotype affects bone turnover rate