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
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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
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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
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REACTION TYPE
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
methyl group transfer
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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.
SYNONYMS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
EC 2.1.1.135
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formerly
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Methionine synthase cob(II)alamin reductase (methylating)
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Methionine synthase reductase
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Methionine synthase reductase
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MSR
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NADPH-dependent diflavin oxidoreductase
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Reductase, methionine synthase
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CAS REGISTRY NUMBER
COMMENTARY
207004-87-3
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ORGANISM
COMMENTARY
LITERATURE
SEQUENCE CODE
SEQUENCE DB
SOURCE
expression by baculovirus-infected insect cells
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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
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-
Manually annotated by BRENDA team
variant I22/L175; variant M22/S175
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Manually annotated by BRENDA team
variant I22/S175; variant M22/S175
Uniprot
Manually annotated by BRENDA team
variant I22M
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Manually annotated by BRENDA team
ACTIVATING COMPOUND
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
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