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C22A
site-directed mutagenesis, the mutation results in severe loss of the enzyme's function
D21A
site-directed mutagenesis, the mutation results in severe loss of the enzyme's function
D21N
site-directed mutagenesis, the mutation results in severe loss of the enzyme's function
K11A
site-directed mutagenesis, the mutant K11A exhibits about 50% reduced redox activity compared to wild-type
H97A
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the mutant shows wild type activity
Q114H
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the mutant shows reduced activity compared to the wild type enzyme
A140D
no alteration in specific activity compared to the wild type enzyme
E155
the deletion causes a 2-3fold increase in the specific activity with each substrate and a significant decrease in the enzyme's heat stability, it is also linked to abnormal arsenic excretion patterns
E208K
no alteration in specific activity compared to the wild type enzyme
N142D
no effect on the specific activity of the enzyme with any substrate
Y34A
complete loss of activity
C29A
site-directed mutagenesis, the mutant shows 8.1fold lower activity with dehydroascorbate compared to wild-type
F28A
site-directed mutagenesis, the mutant shows 2.6fold lower activity with dehydroascorbate compared to wild-type
F30L
site-directed mutagenesis, the mutant shows 6.8fold lower activity with dehydroascorbate compared to wild-type
L225A
site-directed mutagenesis, the mutant shows 3.8fold lower activity with dehydroascorbate compared to wild-type
R176A
site-directed mutagenesis, the mutant shows 3.6fold lower activity with dehydroascorbate compared to wild-type
K47A
the mutant shows about wild type activity
K8A
the mutation significantly reduces the enzymatic activity
D72A
reduction in catalytic efficincy. D72 is a glutathione-site residue
K8A
severe reduction in catalytic efficincy. K8 is a glutathione-site residue
S73A
reduction in catalytic efficincy. S73 is a glutathione-site residue
C23S
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mutant enzyme has almost no activity
C26S
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turnover number is 57% of the wild-type value, KM-value for dehydroascorbate is 2fold lower than the wild-type value, KM-value for GSH is 1.6old lower than the wild-type value
C9S
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turnover number is 86% of the wild-type value, KM-value for dehydroascorbate is 2.8fold lower than the wild-type value, KM-value for GSH is 2fold lower than the wild-type value
C9S/C26S
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turnover number is 43% of the wild-type value, KM-value for dehydroascorbate is 1.1fold higher than the wild-type value, KM-value for GSH is identical to the wild-type value
C25S
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has equivalent specificity constants for dehydroascorbate and GSH, but may have a different catalytic mechanism
additional information
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site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
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site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
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mutant dhar or T-DNA tag line SALK_026089, the expression level of dhar is only one-quarter that in the wild-type, the mutant completely lacks DHAR activity and is highly ozone sensitive
additional information
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overexpression in transgenic Nicotiana tabacum plants, the Arabidopsis enzyme confers resistance to aluminium induced oxidative damage and growth inhibition. Transgenic Nicotiana tabacum plants overexpressing the Arabidosis thaliana DHAR show lower hydrogen peroxide content, less lipid peroxidation and lower level of oxidative DNA damage than wild-type SR-1 plants, overview
additional information
construction of a complete set of single, double and triple mutants carrying T-DNAs in isozymes DHAR1, DHAR2, and DHAR3
additional information
construction of a complete set of single, double and triple mutants carrying T-DNAs in isozymes DHAR1, DHAR2, and DHAR3
additional information
construction of a complete set of single, double and triple mutants carrying T-DNAs in isozymes DHAR1, DHAR2, and DHAR3
additional information
construction of a complete set of single, double and triple mutants carrying T-DNAs in isozymes DHAR1, DHAR2, and DHAR3. No effect on phenotype is observed in the absence of stress. When the different dhar mutant combinations are introduced into a catalase-deficient background (cat2), the combined presence of dhar1 and dhar2 decreased GSSG and total glutathione accumulation. When all 3 DHARs are knocked out, cat2-triggered glutathione oxidation is almost completely inhibited
additional information
construction of a complete set of single, double and triple mutants carrying T-DNAs in isozymes DHAR1, DHAR2, and DHAR3. No effect on phenotype is observed in the absence of stress. When the different dhar mutant combinations are introduced into a catalase-deficient background (cat2), the combined presence of dhar1 and dhar2 decreased GSSG and total glutathione accumulation. When all 3 DHARs are knocked out, cat2-triggered glutathione oxidation is almost completely inhibited
additional information
construction of a complete set of single, double and triple mutants carrying T-DNAs in isozymes DHAR1, DHAR2, and DHAR3. No effect on phenotype is observed in the absence of stress. When the different dhar mutant combinations are introduced into a catalase-deficient background (cat2), the combined presence of dhar1 and dhar2 decreased GSSG and total glutathione accumulation. When all 3 DHARs are knocked out, cat2-triggered glutathione oxidation is almost completely inhibited
additional information
generation of a mutant lacking all three DHAR isozymes (DELTAdhar), the mutant has negligible DHAR activity, but it is shown to be equivalent to wild-type plants in terms of growth and development, as well as ascorbate levels
additional information
generation of a mutant lacking all three DHAR isozymes (DELTAdhar), the mutant has negligible DHAR activity, but it is shown to be equivalent to wild-type plants in terms of growth and development, as well as ascorbate levels
additional information
generation of a mutant lacking all three DHAR isozymes (DELTAdhar), the mutant has negligible DHAR activity, but it is shown to be equivalent to wild-type plants in terms of growth and development, as well as ascorbate levels
additional information
generation of DELTAdhar Arabidopsis plants as well as a quadruple mutant line combining DELTAdhar with an additional vtc2 mutation that causes ascorbate deficiency. Measurements of ascorbate in these mutants under low- or high-light conditions indicate that DHARs have a nonnegligible impact on full ascorbate accumulation under high light, but that they are dispensable when ascorbate concentrations are low to moderate. Because GSH itself can reduce DHA nonenzymatically, the pad2 mutant is used that contains about 30% of the wild-type GSH level. The pad2 mutant accumulates ascorbate at a wild-type level under high light, but when the pad2 mutation is combined with DELTAdhar, there is near-complete inhibition of high-light-dependent ascorbate accumulation. The lack of ascorbate accumulation is consistent with a marked increase in the ascorbate degradation product threonate. These findings indicate that ascorbate recycling capacity is limited in DELTAdhar pad2 plants, and that both DHAR activity and GSH content set a threshold for high-light-induced ascorbate accumulation. Each gene knockout is confirmed by reverse transcription PCR. The measurement of DHAR activity reveals that DHAR1 and DHAR3 are the major isoforms, and that the triple DELTAdhar mutant has negligible DHAR activity. DHAR loss-of-function does not affect MDAR activity
additional information
generation of DELTAdhar Arabidopsis plants as well as a quadruple mutant line combining DELTAdhar with an additional vtc2 mutation that causes ascorbate deficiency. Measurements of ascorbate in these mutants under low- or high-light conditions indicate that DHARs have a nonnegligible impact on full ascorbate accumulation under high light, but that they are dispensable when ascorbate concentrations are low to moderate. Because GSH itself can reduce DHA nonenzymatically, the pad2 mutant is used that contains about 30% of the wild-type GSH level. The pad2 mutant accumulates ascorbate at a wild-type level under high light, but when the pad2 mutation is combined with DELTAdhar, there is near-complete inhibition of high-light-dependent ascorbate accumulation. The lack of ascorbate accumulation is consistent with a marked increase in the ascorbate degradation product threonate. These findings indicate that ascorbate recycling capacity is limited in DELTAdhar pad2 plants, and that both DHAR activity and GSH content set a threshold for high-light-induced ascorbate accumulation. Each gene knockout is confirmed by reverse transcription PCR. The measurement of DHAR activity reveals that DHAR1 and DHAR3 are the major isoforms, and that the triple DELTAdhar mutant has negligible DHAR activity. DHAR loss-of-function does not affect MDAR activity
additional information
generation of DELTAdhar Arabidopsis plants as well as a quadruple mutant line combining DELTAdhar with an additional vtc2 mutation that causes ascorbate deficiency. Measurements of ascorbate in these mutants under low- or high-light conditions indicate that DHARs have a nonnegligible impact on full ascorbate accumulation under high light, but that they are dispensable when ascorbate concentrations are low to moderate. Because GSH itself can reduce DHA nonenzymatically, the pad2 mutant is used that contains about 30% of the wild-type GSH level. The pad2 mutant accumulates ascorbate at a wild-type level under high light, but when the pad2 mutation is combined with DELTAdhar, there is near-complete inhibition of high-light-dependent ascorbate accumulation. The lack of ascorbate accumulation is consistent with a marked increase in the ascorbate degradation product threonate. These findings indicate that ascorbate recycling capacity is limited in DELTAdhar pad2 plants, and that both DHAR activity and GSH content set a threshold for high-light-induced ascorbate accumulation. Each gene knockout is confirmed by reverse transcription PCR. The measurement of DHAR activity reveals that DHAR1 and DHAR3 are the major isoforms, and that the triple DELTAdhar mutant has negligible DHAR activity. DHAR loss-of-function does not affect MDAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. Transgenic Arabidopsis thaliana overexpressing AtDHAR1 maintain higher levels of ascorbate and chlorophyll with reduced levels of membrane damage compared to control plants following exposure to high light, high temperature, or following MV treatment
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. Transgenic Arabidopsis thaliana overexpressing AtDHAR1 maintain higher levels of ascorbate and chlorophyll with reduced levels of membrane damage compared to control plants following exposure to high light, high temperature, or following MV treatment
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. Transgenic Arabidopsis thaliana overexpressing AtDHAR1 maintain higher levels of ascorbate and chlorophyll with reduced levels of membrane damage compared to control plants following exposure to high light, high temperature, or following MV treatment
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. Transgenic expression of AtDHAR2 in tobacco maintains a higher ascorbate level and its oxidation status compared to wild-type plants, resulting in enhanced tolerance to various stresses including ozone, drought, salt, polyethylene glycol (PEG), and aluminium. In Arabidopsis, disruption of DHAR2 decreases the ascorbate redox state but not its pool size, and plants exhibit increased ozone sensitivity, and glutathione oxidation is inhibited in all three dhar single-mutants following photo-oxidative stress
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. Transgenic expression of AtDHAR2 in tobacco maintains a higher ascorbate level and its oxidation status compared to wild-type plants, resulting in enhanced tolerance to various stresses including ozone, drought, salt, polyethylene glycol (PEG), and aluminium. In Arabidopsis, disruption of DHAR2 decreases the ascorbate redox state but not its pool size, and plants exhibit increased ozone sensitivity, and glutathione oxidation is inhibited in all three dhar single-mutants following photo-oxidative stress
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. Transgenic expression of AtDHAR2 in tobacco maintains a higher ascorbate level and its oxidation status compared to wild-type plants, resulting in enhanced tolerance to various stresses including ozone, drought, salt, polyethylene glycol (PEG), and aluminium. In Arabidopsis, disruption of DHAR2 decreases the ascorbate redox state but not its pool size, and plants exhibit increased ozone sensitivity, and glutathione oxidation is inhibited in all three dhar single-mutants following photo-oxidative stress
additional information
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generation of DELTAdhar Arabidopsis plants as well as a quadruple mutant line combining DELTAdhar with an additional vtc2 mutation that causes ascorbate deficiency. Measurements of ascorbate in these mutants under low- or high-light conditions indicate that DHARs have a nonnegligible impact on full ascorbate accumulation under high light, but that they are dispensable when ascorbate concentrations are low to moderate. Because GSH itself can reduce DHA nonenzymatically, the pad2 mutant is used that contains about 30% of the wild-type GSH level. The pad2 mutant accumulates ascorbate at a wild-type level under high light, but when the pad2 mutation is combined with DELTAdhar, there is near-complete inhibition of high-light-dependent ascorbate accumulation. The lack of ascorbate accumulation is consistent with a marked increase in the ascorbate degradation product threonate. These findings indicate that ascorbate recycling capacity is limited in DELTAdhar pad2 plants, and that both DHAR activity and GSH content set a threshold for high-light-induced ascorbate accumulation. Each gene knockout is confirmed by reverse transcription PCR. The measurement of DHAR activity reveals that DHAR1 and DHAR3 are the major isoforms, and that the triple DELTAdhar mutant has negligible DHAR activity. DHAR loss-of-function does not affect MDAR activity
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additional information
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construction of a complete set of single, double and triple mutants carrying T-DNAs in isozymes DHAR1, DHAR2, and DHAR3. No effect on phenotype is observed in the absence of stress. When the different dhar mutant combinations are introduced into a catalase-deficient background (cat2), the combined presence of dhar1 and dhar2 decreased GSSG and total glutathione accumulation. When all 3 DHARs are knocked out, cat2-triggered glutathione oxidation is almost completely inhibited
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additional information
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construction of a complete set of single, double and triple mutants carrying T-DNAs in isozymes DHAR1, DHAR2, and DHAR3
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additional information
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site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. Transgenic Arabidopsis thaliana overexpressing AtDHAR1 maintain higher levels of ascorbate and chlorophyll with reduced levels of membrane damage compared to control plants following exposure to high light, high temperature, or following MV treatment
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additional information
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site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
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site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
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generation of truncated mutants CrDHAR1DELTAN (amino acids 5-226) or CrDHAR1DELTAC (amino acids 1-218)
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generation of truncated mutants CrDHAR1DELTAN (amino acids 5-226) or CrDHAR1DELTAC (amino acids 1-218)
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construcution of different mutants with containing cysteine-to-serine mutations and/or C-terminal residues deleted, kinetic analysis
additional information
construcution of different mutants with containing cysteine-to-serine mutations and/or C-terminal residues deleted, kinetic analysis
additional information
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construcution of different mutants with containing cysteine-to-serine mutations and/or C-terminal residues deleted, kinetic analysis
additional information
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site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. Despite only a small increase in ascorbate content, transgenic Arabidopsis thaliana expressing OsDHAR are more tolerant to salt stress than control plants. Even small changes in DHAR activity may improve tolerance to some environmental stresses
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
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site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
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site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
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construction of overexpressing potato plants overexpressing both the cytosolic and the plastidic isozyme. the trangenic plants overexpressing the cytosolic isozyme show highly increased DHAR activities and ascorbate contents in leaves and tubers, while the plants overexpressing the plastidic isozyme show highly increased DHAR activities and ascorbate contents only in leaves, not in tubers
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity
additional information
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity