EC Number   |
Reaction |
Reference |
|---|
  1.8.5.8 | hydrogen sulfide + glutathione + a quinone = S-sulfanylglutathione + a quinol |
- |
- |
| 1.8.5.8 | hydrogen sulfide + glutathione + a quinone = S-sulfanylglutathione + a quinol |
mechanisms of protein persulfidation, overview |
764484 |
| 1.8.5.8 | hydrogen sulfide + glutathione + a quinone = S-sulfanylglutathione + a quinol |
proposed model for catalysis. The human SQOR reaction is initiated by nucleophilic attack of HS- at the distal cysteine, Cys379, to produce a charge-transfer (CT) complex of FAD with either Cys201S- or Cys379SS- (step 1). Nucleophilic attack of Cys201S- at the C(4a) position of FAD produces a covalent flavin adduct, 4a-adduct I (step 2). Reaction of 4a-adduct I with a sulfane sulfur acceptor (N:) generates 4a-adduct II and the thiolate form of Cys379 (step 3). Nucleophilic attack of Cys379S- at the sulfur atom in the 4a-adduct produces 1,5-dihydroFAD and regenerates the disulfide bridge (step 4). The catalytic cycle is completed upon transfer of electrons from 1,5-dihydro-FAD to CoQ |
765845 |
| 1.8.5.8 | hydrogen sulfide + glutathione + a quinone = S-sulfanylglutathione + a quinol |
the mechanism for sulfide oxidation is catalyzed by an active site cysteine trisulfide. SQR catalyzes two half reactions: (i) sulfur transfer from H2S to an acceptor via an active site cysteine persulfide (Cys-SSH) intermediate, and (ii) electron transfer from H2S to coenzyme Q10 (CoQ10) via an FADH2 intermediate. The first step in the proposed mechanism is addition of the sulfide anion to an active site disulfide between Cys201 and Cys379, generating a persulfide intermediate on Cys379 (379Cys-SSH) with concomitant release of the Cys201 thiolate. Formation of an electronic species is detected that is distinct from those seen in other members of the flavin disulfide reductase superfamily. In the final step, electron transfer to CoQ10 regenerates FAD and connects SQR to the electron transfer chain at the level of complex III. Reaction mechanism, overview |
764431 |
| 1.8.5.8 | hydrogen sulfide + glutathione + a quinone = S-sulfanylglutathione + a quinol |
the reaction cycle proceeds via two half reactions. In the first half reaction, sulfide adds to the trisulfide at the solvent-accessible Cys379 to form a 379Cys-SSH persulfide. The bridging sulfur is retained on 201Cys-SS- persulfide, which forms an unusually intense charge transfer (CT) complex with FAD. Sulfur transfer from 379Cys-SSH to a small molecule acceptor leads to regeneration of the active site trisulfide with the concomitant two-electron reduction of FAD. In the second half reaction, FADH2 transfers electrons to CoQ10, regenerating the resting enzyme and linking sulfide oxidation to mitochondrial energy metabolism by supplying reduced CoQ10 to Complex III in the electron transport chain |
764977 |
