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Literature summary for 1.16.1.8 extracted from

  • Meints, C.E.; Parke, S.M.; Wolthers, K.R.
    Proximal FAD histidine residue influences interflavin electron transfer in cytochrome P450 reductase and methionine synthase reductase (2014), Arch. Biochem. Biophys., 547, 18-26 .
    View publication on PubMed
Search for more literature for 1.16.1.8

Cloned(Commentary)

Cloned (Comment) Organism
recombinant expression of wild-type and mutant enzymes in Escherichia coli strain Rosetta2(DE3)pLysS Homo sapiens

Protein Variants

Protein Variants Comment Organism
A312H site-directed mutangenesis, mutation of the catalytic residue leads to the kinetic coupling of hydride and interflavin electron transfer, and eliminates the formation of the FAD hydroquinone intermediate, substitution of Ala312 for His in MSR weakens NADP(H) binding as the Km for NADPH and Ki for NADP+ increases 6 and 1.7fold, respectively. NADPH reduction of A312H resembles that of native cytochrome P450 reductase, in that it occurs in two discrete kinetic phases, without the transient formation of the E-FADH2-FMN intermediate Homo sapiens
A312Q site-directed mutangenesis, the catalytic site mutant shows a 2.5fold increased Km and a slightly decreased Ki for the coenzyme FAD Homo sapiens

Inhibitors

Inhibitors Comment Organism Structure
NADP+
-
 Homo sapiens

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
 additional information stopped-flow and steady-state kinetic analysis Homo sapiens
0.0024
-
 NADPH pH 7.5, 25°C, recombinant wild-type enzyme Homo sapiens
0.0062
-
 NADPH pH 7.5, 25°C, recombinant mutant A312Q Homo sapiens
0.015
-
 NADPH pH 7.5, 25°C, recombinant mutant A312H Homo sapiens

Natural Substrates/ Products (Substrates)

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

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 hydride transfer and interflavin electron transfer are two catalytic steps represented by two distinct kinetic phases leading to transient formation of the FAD hydroquinone Homo sapiens
a

Substrates and Products (Substrate)

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

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

Turnover Number [1/s]

Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
3.6
-
 NADPH pH 7.5, 25°C, recombinant mutant A312H Homo sapiens
7.2
-
 NADPH pH 7.5, 25°C, recombinant wild-type enzyme Homo sapiens
7.8
-
 NADPH pH 7.5, 25°C, recombinant mutant A312Q Homo sapiens

pH Optimum

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

Cofactor

Cofactor Comment Organism Structure
FAD the proximal FAD histidine residue accelerates proton-coupled electron transfer from FADH2 to the higher potential FMN Homo sapiens
FMN the proximal FAD histidine residue accelerates proton-coupled electron transfer from FADH2 to the higher potential FMN Homo sapiens
additional information mechanism of NADPH reduction of a diflavin enzyme, overview Homo sapiens
NADPH
-
 Homo sapiens

Ki Value [mM]

Ki Value [mM] Ki Value maximum [mM] Inhibitor Comment Organism Structure
0.0291
-
 NADP+ pH 7.5, 25°C, recombinant mutant A312Q Homo sapiens
0.0369
-
 NADP+ pH 7.5, 25°C, recombinant wild-type enzyme Homo sapiens
0.0729
-
 NADP+ pH 7.5, 25°C, recombinant mutant A312H Homo sapiens