1.8.5.8: eukaryotic sulfide quinone oxidoreductase
This is an abbreviated version!
For detailed information about eukaryotic sulfide quinone oxidoreductase, go to the full flat file.
Reaction
Synonyms
glutathione:CoQ reductase, HMT2, ScSQR, SQOR, SQR, Sqrdl, sulfide : quinone oxidoreductase, sulfide quinone oxidoreductase, sulfide:quinone oxidoreductase
ECTree
1.8.5.8 eukaryotic sulfide quinone oxidoreductaseAdvanced search results
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Substrates Products on EC 1.8.5.8 - eukaryotic sulfide quinone oxidoreductase
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SUBSTRATE 
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
hydrogen sulfide + CoA + coenzyme Q1
CoA-SSH + H+ + reduced coenzyme Q1
-
-
-
?
hydrogen sulfide + coenzyme Q1
hydrogen disulfide + reduced coenzyme Q1
-
-
-
?
hydrogen sulfide + glutathione + coenzyme Q1
glutathione persulfide + H+ + reduced coenzyme Q1
-
-
-
?
hydrogen sulfide + glutathione + coenzyme Q1
S-sulfanylglutathione + reduced coenzyme Q1
-
-
-
?
hydrogen sulfide + glutathione + coenzyme Q10
S-sulfanylglutathione + reduced coenzyme Q10
-
-
-
?
hydrogen sulfide + glutathione + ubiquinone
S-sulfanylglutathione + ubiquinol
-
-
-
ir
hydrogen sulfide + sulfite + coenzyme Q1
thiosulfate + reduced coenzyme Q1
-
-
-
?
Na2S + glutathione + coenzyme Q1
S-sulfanylglutathione + reduced coenzyme Q1 + 2 Na+
-
-
-
?
hydrogen sulfide + glutathione + a quinone
S-sulfanylglutathione + a quinol
-
-
-
?
hydrogen sulfide + glutathione + a quinone
S-sulfanylglutathione + a quinol
-
-
-
?
hydrogen sulfide + glutathione + a quinone
S-sulfanylglutathione + a quinol
-
-
-
-
?
hydrogen sulfide + glutathione + a quinone
S-sulfanylglutathione + a quinol
-
-
-
?
hydrogen sulfide + glutathione + coenzyme Q
S-sulfanylglutathione + reduced coenzyme Q
-
-
-
?
hydrogen sulfide + glutathione + coenzyme Q
S-sulfanylglutathione + reduced coenzyme Q
-
-
-
ir
hydrogen sulfide + glutathione + decylubiquinone
S-sulfanylglutathione + decylubiquinol
-
-
-
?
hydrogen sulfide + glutathione + decylubiquinone
S-sulfanylglutathione + decylubiquinol
-
-
-
ir
hydrogen sulfide + glutathione + decylubiquinone
S-sulfanylglutathione + decylubiquinol
-
-
-
ir
hydrogen sulfide + glutathione + decylubiquinone
S-sulfanylglutathione + decylubiquinol
-
-
-
ir
hydrogen sulfide + glutathione + quinone
S-sulfanylglutathione + quinol
-
-
-
?
hydrogen sulfide + glutathione + quinone
S-sulfanylglutathione + quinol
-
-
-
ir
hydrogen sulfide + glutathione + quinone
S-sulfanylglutathione + quinol
-
-
-
ir
hydrogen sulfide + glutathione + quinone
S-sulfanylglutathione + quinol
-
-
-
ir
additional information
?
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no activity with DHLA, cysteamine, coenzyme A, hypotaurine, cysteine sulfinic acid, and thioredoxin
-
-
?
additional information
?
-
under physiological conditions, the primary sulfane sulfur acceptor for the SQOR reaction is GSH, generating glutathione persulfide (GSSH) as the product. Substrate promiscuity leads to dead-end complexes. Human SQOR exhibits remarkable substrate promiscuity, and in addition to sulfide, a number of nucleophiles can add to the resting trisulfide. The addition of alternative nucleophiles to resting SQOR leads to the corresponding 379Cys mixed disulfide and the 201Cys-SS- persulfide that forms an intense charge transfer (CT) complex with FAD. Unlike the sulfide-induced CT complex, which decays quickly to yield FADH2, the alternative CT complexes represent dead-end complexes and decay slowly at rates that approximate the respective dissociation rate constants (koff) for the nucleophiles. Although these dead-end complexes could entrap SQOR in an unproductive state, their formation is suppressed to some extent by the membrane environment of SQOR
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-
additional information
?
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CoQ-binding pocket and substrate binding structures, overview. The entrance to the CoQ-binding pocket is located on the membrane-facing surface of human SQOR
-
-
-
additional information
?
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SQOR accommodates alternative sulfane sulfur acceptors, e.g. small thiophilic acceptors. Structural basis for substrate promiscuity, overview
-
-
-
additional information
?
-
the rate of sulfide addition to the cysteine trisulfide of SQOR is estimated to much higher than the rate of sulfide addition to cysteine disulfide in solution. The subsequent formation of persulfide rather than thiolate intermediate on Cys201 also enhances its reactivity for facilitating sulfur transfer and electron movement via the putative C4a adduct. Computational modeling, overview
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additional information
?
-
the substrate promiscuity of SQR is expanded to include CoA as an alternate sulfur acceptor, forming CoA-SSH. Postulation of a different mechanism for human SQR by assigning the 201Cys-SS- (versus the Cys201 thiolate) as the species involves in charge-transfer (CT) complex formation with FAD, and 379Cys-SSH as the sulfane sulfur donor to an external acceptor. Since the absorption spectrum of CoA interfers with monitoring CoQ1 reduction at 278 nm in the steady-state SQR assay, an alternative coupled assay is developed using persulfide dioxygenase (PDO), which oxidizes CoA-SSH in an O2-dependent reaction. Michaelis-Menten analysis of SQR activity at varying CoA concentrations, overview
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