EC Number   |
General Information |
Reference |
|---|
   1.8.5.1 | evolution |
DHA reductase (DHAR) belongs to the glutathione S-transferase (GST) superfamily. Unlike most other GSTs, DHARs have an active-site cysteine in place of serine, and rather than stabilizing the thiolate anion of GSH (GS-), this change confers the capacity for reversible disulfide bond formation with GSH as part of the catalytic mechanism |
-, 765156 |
| 1.8.5.1 | malfunction |
a mutant lacking all three DHAR isozymes (DELTAdhar), with negligible DHAR activity, is shown to be equivalent to wild-type plants in terms of growth and development, as well as ascorbate levels. Analysis of the DELTAdhar mutant shows that DHARs are required to couple hydrogen peroxide metabolism to glutathione oxidation and that this is functionally important for downstream activation of the salicylic acid pathway. Thus, the role of DHARs in ascorbate recycling remains controversial. DHAR activity is dispensable for growth and ascorbate homeostasis under low light. When subjected to high-light stress, both the wild-type plants and DELTAdhar mutants accumulate ascorbate to high levels, but minor differences are observed after a prolonged stress. The lower ascorbate accumulation of DELTAdhar relative to the wild-type is associated with a slight overaccumulation of threonate, an ascorbate degradation. A blockage of ascorbate accumulation in response to high light is also observed when glutathione deficiency is induced pharmacologically by buthionine sulfoximine treatment, providing extra evidence that, in high-light conditions, glutathione acts as a substitute for ascorbate reduction |
765592 |
| 1.8.5.1 | malfunction |
DHAR overexpression in maize leads to an increase in ascorbate and glutathione concentration, as well as a shift toward the reduced state for glutathione |
765592 |
| 1.8.5.1 | malfunction |
DHAR-downregulated tobacco lines show reduced total ascorbate levels, lower dry weight, and diminished photosynthetic efficiency. DHAR overexpression in tobacco leads to an increase in ascorbate and glutathione concentration, as well as a shift toward the reduced state for glutathione |
765592 |
| 1.8.5.1 | malfunction |
multiple loss of DHAR functions markedly decreases glutathione oxidation triggered by catalase deficiency. No evidence is obtained that either GRs or MDHARs are upregulated in plants lacking DHAR function. 3-Aminotriazole (3-AT) decreases catalase to very low levels while inducing ascorbate peroxidase (APX) and DHAR activities. These effects are accompanied by extensive leaf bleaching, and glutathione oxidation is evident as marked accumulation of GSSG. No difference is observed in bleaching or glutathione contents between the wild-type control and any of the mutants. Loss-of-function mutants for DHAR suggest that ascorbate regeneration is the major route leading to GSSG accumulation in response to intracellular H2O2. 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 DHAR isozymes (DHAR1-3) are knocked out, cat2-triggered glutathione oxidation is almost completely inhibited. Similar effects are observed in dhar1/dhar2 and dhar1/dhar2/dhar3 mutants using 3-AT to inhibit catalase. The major contribution to both lesion formation and glutathione oxidation triggered by catalase deficiency appears to come from DHAR1 and DHAR2 with a minor but significant contribution from chloroplastic DHAR3 |
-, 765624 |
| 1.8.5.1 | malfunction |
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity |
-, 765156 |
| 1.8.5.1 | malfunction |
site-directed mutagenesis of the catalytic cysteine abolishes DHAR activity. 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 |
765156 |
| 1.8.5.1 | malfunction |
the increase of AsA regeneration via enhanced DHAR activity modulates the ascorbate-glutathione cycle activity against photooxidative stress in Chlamydomonas reinhardtii |
765604 |
| 1.8.5.1 | metabolism |
glutathione is a pivotal molecule in oxidative stress, during which it is potentially oxidized by several pathways linked to H2O2 detoxification. Response and functional importance of 3 potential routes for glutathione oxidation pathways mediated by glutathione S-transferases (GST), glutaredoxin-dependent peroxiredoxins (PRXII), and dehydroascorbate reductases (DHAR) in Arabidopsis during oxidative stress, overview. Interplay between different DHARs appears to be necessary to couple ascorbate and glutathione pools and to allow glutathione-related signaling during enhanced H2O2 metabolism |
-, 765624 |
| 1.8.5.1 | metabolism |
isoform DHAR3 contributes, at least to some extent, to ascorbate recycling |
742122 |
