EC Number   |
Reaction |
Reference |
|---|
   1.8.5.1 | 2 glutathione + dehydroascorbate = glutathione disulfide + ascorbate |
catalytic mechanism |
394032 |
| 1.8.5.1 | 2 glutathione + dehydroascorbate = glutathione disulfide + ascorbate |
the reaction of DHAR proceeds by a bi-uni-uni-uniping-pong enzymatic mechanism. In step 1, the DHA molecule is bound to the catalytic cysteine residue of the reduced form of DHAR (DHAR-S-) and is reduced to ascorbate. This reduction involves nucleophilic attack by the catalytic cysteine residue and the formation of cysteine sulfenic acid (sulfenylated DHAR, DHAR-SOH). In step 2, the reactive sulfenic acid at the catalytic cysteine residue reacts with GSH bound at the G-site and generates the mixed disulfide (DHAR-S-SG). Subsequently, the second GSH molecule binds to the H-site and may be de-protonated to GS-. Then, the GSH bound with the catalytic cysteine residue is removed by the nucleophilic attack of GS- at the H-site. As a result, a catalytic cysteine residue is reduced and one molecule of glutathione disulfide (GSSG) is released (step 3). 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 | 2 glutathione + dehydroascorbate = glutathione disulfide + ascorbate |
the reaction of DHAR proceeds by a bi-uni-uni-uniping-pong enzymatic mechanism. In step 1, the DHA molecule is bound to the catalytic cysteine residue of the reduced form of DHAR (DHAR-S-) and is reduced to ascorbate. This reduction involves nucleophilic attack by the catalytic cysteine residue and the formation of cysteine sulfenic acid (sulfenylated DHAR, DHAR-SOH). In step 2, the reactive sulfenic acid at the catalytic cysteine residue reacts with GSH bound at the G-site and generates the mixed disulfide (DHAR-S-SG). Subsequently, the second GSH molecule binds to the H-site and may be deprotonated to GS-. Then, the GSH bound with the catalytic cysteine residue is removed by the nucleophilic attack of GS- at the H-site. As a result, a catalytic cysteine residue is reduced and one molecule of glutathione disulfide (GSSG) is released (step 3). 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 |
