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Literature summary for 1.16.1.8 extracted from

  • Meints, C.E.; Simtchouk, S.; Wolthers, K.R.
    Aromatic substitution of the FAD-shielding tryptophan reveals its differential role in regulating electron flux in methionine synthase reductase and cytochrome P450 reductase (2013), FEBS J., 280, 1460-1474.
    View publication on PubMed

Protein Variants

Protein Variants Comment Organism
W697F 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 Homo sapiens
W697Y 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 Homo sapiens

Inhibitors

Inhibitors Comment Organism Structure
2',5'-ADP competitive inhibition Homo sapiens
NADP+ competitive inhibition in the reaction with NADPH and cytochrome c3+ as substrates, overview Homo sapiens

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
additional information steady-state kinetics analysis of wild-type and mutant enzymes with cytochrome c3+ and NADPH as substrates, overview Homo sapiens

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
2 [methionine synthase]-methylcob(I)alamin + 2 S-adenosylhomocysteine + NADP+ Homo sapiens
-
2 [methionine synthase]-cob(II)alamin + NADPH + H+ + 2 S-adenosyl-L-methionine
-
?

Organism

Organism UniProt Comment Textmining
Homo sapiens Q9UBK8
-
-

Reaction

Reaction Comment Organism Reaction ID
2 [methionine synthase]-methylcob(III)alamin + 2 S-adenosyl-L-homocysteine + NADP+ = 2 [methionine synthase]-cob(II)alamin + NADPH + H+ + 2 S-adenosyl-L-methionine mechanism for the NADPH-catalyzed reduction of diflavin oxidoreductases, overview Homo sapiens

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
2 [methionine synthase]-methylcob(I)alamin + 2 S-adenosylhomocysteine + NADP+
-
Homo sapiens 2 [methionine synthase]-cob(II)alamin + NADPH + H+ + 2 S-adenosyl-L-methionine
-
?
2 [methionine synthase]-methylcob(I)alamin + 2 S-adenosylhomocysteine + NADP+ the enzyme transfers reducing equivalents from NADPH via an FAD and FMN cofactor to a redox partner protein. hydride transfer from NADPH to FAD requires displacement of a conserved tryptophan that lies coplanar to the FAD isoalloxazine ring Homo sapiens 2 [methionine synthase]-cob(II)alamin + NADPH + H+ + 2 S-adenosyl-L-methionine
-
?
additional information the enzyme catalyzes the reduction of cytochrome c3+ with NADPH and NADH Homo sapiens ?
-
?

Synonyms

Synonyms Comment Organism
Methionine synthase reductase
-
Homo sapiens
MSR
-
Homo sapiens

Temperature Optimum [°C]

Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
25
-
assay at Homo sapiens

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
7.5
-
assay at Homo sapiens

Cofactor

Cofactor Comment Organism Structure
FAD
-
Homo sapiens
FMN
-
Homo sapiens
NADP+
-
Homo sapiens

Ki Value [mM]

Ki Value [mM] Ki Value maximum [mM] Inhibitor Comment Organism Structure
0.0001
-
2',5'-ADP pH 7.5, 25°C, mutant W697F, with cytochrome c3+ Homo sapiens
0.0007
-
2',5'-ADP pH 7.5, 25°C, mutant W697Y, with cytochrome c3+ Homo sapiens
0.0014
-
2',5'-ADP pH 7.5, 25°C, wild-type enzyme Homo sapiens
0.003
-
NADP+ pH 7.5, 25°C, mutant W697F, with cytochrome c3+ Homo sapiens
0.0042
-
NADP+ pH 7.5, 25°C, mutant W697Y, with cytochrome c3+ Homo sapiens
0.037
-
NADP+ pH 7.5, 25°C, wild-type enzyme Homo sapiens