Information on EC 1.16.1.1 - mercury(II) reductase

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

EC NUMBER
COMMENTARY hide
1.16.1.1
-
RECOMMENDED NAME
GeneOntology No.
mercury(II) reductase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
Hg + NADP+ + H+ = Hg2+ + NADPH
show the reaction diagram
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
redox reaction
-
-
-
-
PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
phenylmercury acetate degradation
SYSTEMATIC NAME
IUBMB Comments
Hg:NADP+ oxidoreductase
A dithiol enzyme.
CAS REGISTRY NUMBER
COMMENTARY hide
67880-93-7
-
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
TFI 29
-
-
Manually annotated by BRENDA team
isolated from surface and sub-surface floodplain soil, Oak Ridge, USA, gene merA
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-
Manually annotated by BRENDA team
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-
-
Manually annotated by BRENDA team
Alcanivorax sp.
Alcanivorax sp. EPR
strain EPR 10 resistant to up to 0.075 mM Hg2+
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-
Manually annotated by BRENDA team
Alcanivorax sp. EPR5
strain EPR5 resistant to up to 0.01 mM Hg2+
-
-
Manually annotated by BRENDA team
Alcanivorax sp. EPR6
strain EPR6 resistant to up to 0.075 mM Hg2+
SwissProt
Manually annotated by BRENDA team
strain EPR7, resistant to up to 0.075 mM Hg2+
SwissProt
Manually annotated by BRENDA team
Alcanivorax sp. EPR8
strain EPR8, resistant to up to 0.075 mM Hg2+
SwissProt
Manually annotated by BRENDA team
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-
-
Manually annotated by BRENDA team
SS2
-
-
Manually annotated by BRENDA team
strain RC607
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-
Manually annotated by BRENDA team
Citrobacter sp.
-
-
-
Manually annotated by BRENDA team
-
-
-
Manually annotated by BRENDA team
PWS1
-
-
Manually annotated by BRENDA team
Flavobacterium rigense
strain PR2
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-
Manually annotated by BRENDA team
Flavobacterium rigense PR2
strain PR2
-
-
Manually annotated by BRENDA team
strain resistant to up to 0.04 mM Hg2+
-
-
Manually annotated by BRENDA team
Hydrogenivirga sp.
-
UniProt
Manually annotated by BRENDA team
Hydrogenobaculum sp.
-
UniProt
Manually annotated by BRENDA team
i.e. Bacillus sphaericus, isolated from an industrial mercuric salt-contaminated soil, gene merA
UniProt
Manually annotated by BRENDA team
strain resistant to up to 0.05 mM Hg2+
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-
Manually annotated by BRENDA team
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-
-
Manually annotated by BRENDA team
enzyme is encoded by the plasmid pVT1
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-
Manually annotated by BRENDA team
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-
-
Manually annotated by BRENDA team
Oerskovia sp.
-
-
-
Manually annotated by BRENDA team
MR-2 strain
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-
Manually annotated by BRENDA team
MR-2 strain
-
-
Manually annotated by BRENDA team
plasmid R100
strain PAO 9501
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-
Manually annotated by BRENDA team
PAO9501
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-
Manually annotated by BRENDA team
Pseudomonas aeruginosa PAO9501 (pVS1)
PAO9501 (pVS1)
-
-
Manually annotated by BRENDA team
Pseudomonas putida KT2442::mer-73
KT2442::mer-73
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-
Manually annotated by BRENDA team
marine-isolated mercury-resistant strain, isolated from seawater collected from Yantai coastal zone in Shandong Province, China, gene merA encoded in the mer operon
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-
Manually annotated by BRENDA team
gene merA from the Tn21 mer operon
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-
Manually annotated by BRENDA team
strain M130
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-
Manually annotated by BRENDA team
strain M130
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-
Manually annotated by BRENDA team
strain 5
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-
Manually annotated by BRENDA team
strain 5
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-
Manually annotated by BRENDA team
strain 1326; strain 8
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-
Manually annotated by BRENDA team
strain 1326
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-
Manually annotated by BRENDA team
strain 8
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-
Manually annotated by BRENDA team
isolated from surface and sub-surface floodplain soil, Oak Ridge, USA, gene merA
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-
Manually annotated by BRENDA team
isolated from surface and sub-surface floodplain soil, Oak Ridge, USA, gene merA
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-
Manually annotated by BRENDA team
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-
-
Manually annotated by BRENDA team
Yersinia enterolytica
138A14
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-
Manually annotated by BRENDA team
Yersinia enterolytica 138A14
138A14
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-
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
evolution
organomercurials are converted to less toxic Hg(0) in the cytosol by the sequential action of organomercurial lyase MerB and mercuric ion reductase MerA, requiring transfer of Hg(II) from MerB to MerA, with transfer to the metallochaperone-like NmerA domain as the kinetically favored pathway in this coevolved system, overview. Hg(II) removal from MerB by the N-terminal domain, NmerA, and catalytic core C-terminal cysteine pairs of its coevolved MerA and by GSH, the major competing cellular thiol in gamma-proteobacteria. The reaction with a 10fold excess of NmerA over HgMerB removes about 92% of Hg(II), while similar extents of reaction require more than 1000fold excess of GSH
physiological function
additional information
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
2,4,6-trinitrobenzenesulfonate + NADPH
? + NADP+
show the reaction diagram
Hg + NAD+ + H+
Hg2+ + NADH
show the reaction diagram
Hg + NADP+ + H+
Hg2+ + NADPH
show the reaction diagram
Hg2+ + azure A
Hg + ?
show the reaction diagram
Hg2+ + NADH
Hg + NAD+ + H+
show the reaction diagram
Hg2+ + NADPH
Hg + NADP+ + H+
show the reaction diagram
Hg2+ + NADPH
Hg(0) + NADP+
show the reaction diagram
Hg2+ + neutral red
Hg + ?
show the reaction diagram
merthiolate + NADPH
? + NADP+
show the reaction diagram
NADPH + Hg2+
NADP+ + Hg
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
Hg + NAD+ + H+
Hg2+ + NADH
show the reaction diagram
Hg + NADP+ + H+
Hg2+ + NADPH
show the reaction diagram
Hg2+ + NADPH
Hg + NADP+ + H+
show the reaction diagram
Hg2+ + NADPH
Hg(0) + NADP+
show the reaction diagram
additional information
?
-
E0XF09
proposed model for reaction of NmerA with HgMerB and of GSH with HgMerB, overview
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-
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
additional information
the enzymes contains FAD, utilizes NADPH as an electron donor, and requires an excess of exogenous thiols for activity
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
Ag2+
Yersinia enterolytica
-
-
Cl-
-
inhibitory above 0.1 M, complete inhibition at 1 M
KCN
Flavobacterium rigense
-
0.1 mM, 20% inhibition
Mn2+
Yersinia enterolytica
-
weak inhibition
NADPH
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substrate inhibition of the reaction with 2,4,6-trinitrobenzenesulfonate and NADPH
Pb(NO3)2
Flavobacterium rigense
-
0.1 mM, 78% inhibition
Pb2+
-
0.1 mM, 60% inhibition
additional information
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
2-mercaptoethanol
cysteine
dithiothreitol
-
thiol compound required
NADPH
-
100 microM, 30 min preincubation, relative initial rate 151%, 10 min preincubation with NADPH results in an increase of reactive thiol groups
thioglycolate
-
thiol compound required
thiol
-
exogenous thiols are required for catalytic reduction of Hg(II) to Hg2+, due to prevention or reversal of formation of an abortive complex of Hg(II) with the thiol/thiolate pair of two-electron reduced enzyme
additional information
-
0.1 mM NADP+ stimulates the 2,4,6-trinitrobenzenesulfonate-dependent NADPH oxidation more than 10fold
-
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.0019 - 75
Hg2+
0.0088 - 0.2
HgCl2
0.0004
NADPH
-
25C, pH 7.3; in presence of 1 mM cysteine
additional information
additional information
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.383 - 13.5
Hg2+
12.4
HgCl2
Acidithiobacillus ferrooxidans
-
-
additional information
additional information
Pseudomonas aeruginosa
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-
-
Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.016
Ag2+
Yersinia enterolytica
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-
0.018
Cu2+
Yersinia enterolytica
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-
0.0175
Ni2+
Yersinia enterolytica
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-
IC50 VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.27
Hg2+
uncultured bacterium
V5TDP2
pH 7.4, 37C
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
0.13
cell extract, mercury-dependent oxidation of NADPH, pH 7.4, 25C
2.08
Yersinia enterolytica
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-
6.8
Flavobacterium rigense
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-
additional information
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-
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
7.5 - 8
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-
pH RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
5 - 9
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high activity within that range
6.5 - 9
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pH 6.5: about 60% of maximal activity, pH 9.0: about 50% of maximal activity
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
28
-
assay at
37 - 43
Yersinia enterolytica
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-
50
Hydrogenobaculum sp.
-
70
Hydrogenivirga sp.
-
TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
30 - 70
Hydrogenobaculum sp.
activity range, very low activity below 40C
60 - 87
Hydrogenivirga sp.
activity range, very low activities below 40C
pI VALUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
5
-
isoelectric focusing
5.1
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isoelectric focusing
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
additional information
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
58000
-
gel filtration
110000
-
gel filtration
123000
-
gel filtration
130000
-
gel filtration
142000
-
gel filtration
190000
200000
Yersinia enterolytica
-
gel filtration
additional information
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
homodimer
monomer
trimer
additional information
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
hanging-drop vapor-diffusion method
-
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
60
10 min, 80% activity remaining
75
10 min, 50% inactivation
100
Yersinia enterolytica
-
15 min, complete inactivation
additional information
the mercuric reductase is stable at high temperatures
GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
immobilization of the enzyme appears to significantly enhance storage stability
-
operational stability: after 1.5 h decline of activity up to 20%
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stable to repeated freeze-thaw cycles
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OXIDATION STABILITY
ORGANISM
UNIPROT
LITERATURE
activated enzyme appears to be stable under anaerobic conditions and eventually returns to the original level of activity in the presence of oxygen. The activated state seems to be stabilized by 1mM cysteine.
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438069
STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
4C, 50 mM potassium phosphate buffer, pH 7.2, 0.5 mM EDTA, 1% 2-mercaptoethanol, half-life of soluble enzyme is 3 weeks, immobilized enzyme shows large decline at the beginning and almost no further decrease of activity after 3 weeks
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
purification of the major 14C-labeled peptide from a tryptic digestion of labeled mercuric reductase
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recombinant enzyme
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recombinant His-tagged MerA from Escherichia coli strain BL21(DE3)Plys by nickel affinity chromatography
plasmid R100
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recombinant MerA catalytic core and NmerA proteins from Escherichia coli strain XL-1 Blue by anion exchange chromatography and gel filtreation, and separation by affinity chromatography
recombinant wild-type and mutant N-terminally His6-tagged and maltose-binding protein fusion enzymes from Escherichia coli strain C43 by amylose affinity chromatography, cleavage of the tags by 3C protease, ultrafiltration, and gel filtration
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
cloned and expressed constitutively in Escherichia coli
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expression in Escherichia coli
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gene merA and mer operon, expression of MerA catalytic core and NmerA proteins in Escherichia coli strain XL-1 Blue
gene merA, DNA and amino acid sequence determination and analysis, phylogenetic analysis
gene merA, DNA and amino acid sequence determination and analysis, pylogenetic analysis and tree, recombinant expression in Escherichia coli strain BL21(DE3)
gene merA, expression as wild-type and mutant N-terminally His6-tagged and maltose-binding protein fusion proteins with a 3C protease cleavage site in Escherichia coli strain TOP10 and C43
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gene merA, mer operon located on Tn5041, DNA and amino acid sequence determination and analysis, chromosomal localization, real-time PCR enzyme expression analysis
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gene merA, recombinant expression in transgenoc Nicotiana tabacum cv. Xanthium plants using gene transfer by Agrobacterium tumefaciens. Transgenic tobacco expressing merA volatilizes significantly more mercury than wild-type plants. Subcloning in Escherichia coli strains DH5alpha and BL21(DE3)
plasmid R100
gene merA, the MerA protein is encoded by the mer operon on transposon Tn501, DNA and amino acid sequence determination and analysis, sequence comparisons and phylogenetic analysis
merA, DNA and amino acid sequence determination of genes from bacteria isolated from surface and sub-surface floodplain soil, phylogenetic analysis, overview
plasmid transfer to mercury sensitive Escherichia coli strain DH5alpha, overexpression of gene merA as His-tagged protein in Escherichia coli BL21(DE3)Plys cells
plasmid R100
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subcloning and expression in strain TG2, bacterial two hybrid assays are performed in strain BTH101
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
the enzyme is induced by Hg
transcriptional level of merA increased 157fold and 255 fold after 30 min after 60 min of incubation with 6 microM HgCl2+, respectively; transcriptional level of merA increased 197fold after incubation with 1 microM CdCl2+
-
transcriptional level of merA increased 30fold and 45fold after treatment with 10 microM ZnCl2+ and 30 microM ZnCl2+, respectively
-
transcriptional level of merA increased 6, 10, and 20fold after treatment with 5, 10, and 20 microM CdSO4 2+, respectively
ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
C628A
-
HgX2 substrates with small ligands can rapidly access the redox-active cysteines in the absence of the C-terminal cysteines, but those with large ligands require the C-terminal cysteines for rapid access. The C-terminal cysteines play a critical role in removing the high-affinity ligands before Hg(II) reaches the redox-active cysteines
C629A
-
HgX2 substrates with small ligands can rapidly access the redox-active cysteines in the absence of the C-terminal cysteines, but those with large ligands require the C-terminal cysteines for rapid access. The C-terminal cysteines play a critical role in removing the high-affinity ligands before Hg(II) reaches the redox-active cysteines
Y264F
-
Km-value for Hg2+ is 5fold lower compared to the Km-value of the wild-type enzyme, turn-over number is reduced by 164fold
Y264F/Y605F
-
Km-value for Hg2+ is 5fold lower than the Km-value of the wild-type enzyme, turnover-number is reduced by 1091fold
Y605F
-
Km-value for Hg2+ is 1.3fold higher compared to the Km-value of the wild-type enzyme, turnover-number is reduced by 6.3fold
C628A
-
HgX2 substrates with small ligands can rapidly access the redox-active cysteines in the absence of the C-terminal cysteines, but those with large ligands require the C-terminal cysteines for rapid access. The C-terminal cysteines play a critical role in removing the high-affinity ligands before Hg(II) reaches the redox-active cysteines
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C629A
-
HgX2 substrates with small ligands can rapidly access the redox-active cysteines in the absence of the C-terminal cysteines, but those with large ligands require the C-terminal cysteines for rapid access. The C-terminal cysteines play a critical role in removing the high-affinity ligands before Hg(II) reaches the redox-active cysteines
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Y264F
-
Km-value for Hg2+ is 5fold lower compared to the Km-value of the wild-type enzyme, turn-over number is reduced by 164fold
-
Y264F/Y605F
-
Km-value for Hg2+ is 5fold lower than the Km-value of the wild-type enzyme, turnover-number is reduced by 1091fold
-
Y605F
-
Km-value for Hg2+ is 1.3fold higher compared to the Km-value of the wild-type enzyme, turnover-number is reduced by 6.3fold
-
C558A
-
mutation results in a total disruption of the Hg(II) detoxification pathway in vivo, compared to wild-type enzyme the mutant shows a 20fold reduction in turnover number and a 10fold increase in Km
C559A
-
mutation results in a total disruption of the Hg(II) detoxification pathway in vivo, compared to wild-type enzyme less than a 2fold reduction in turnover number and an increase in Km-value of 4-5fold
Y605H
-
24fold decrease in turnover number and a 15fold decrease in Km-value
C11A
-
site-directed mutagenesis of NmerA residue of the metal binding site
C14A
-
site-directed mutagenesis of NmerA residue of the metal binding site
Y62F
-
site-directed mutagenesis of NmerA residue of the metal binding site
C135A
-
site-directed mutagenesis
C140A
-
site-directed mutagenesis
C14A
-
site-directed mutagenesis
C561A
-
site-directed mutagenesis
E133G/E134G
site-directed mutagenesis, the mutant shows altered salt and metal resistance and temperature stability compared to the wild-type enzyme
E15A/E16A
site-directed mutagenesis, the mutant shows altered salt and metal resistance and temperature stability compared to the wild-type enzyme
E515A/E516A
site-directed mutagenesis, the mutant shows altered salt and metal resistance and temperature stability compared to the wild-type enzyme
E545A/E546A
site-directed mutagenesis, the mutant shows salt and metal resistance and temperature stability similar to the wild-type enzyme
K432L/P433D/A434L/R435T
site-directed mutagenesis, the mutant shows salt and metal resistance and temperature stability similar to the wild-type enzyme
K432L/P433D/A434L/R435T/K465D/V466S/G467R/K468T/F469L/P470T
site-directed mutagenesis, the mutant shows salt and metal resistance and temperature stability similar to the wild-type enzyme
additional information
APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
environmental protection
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