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Literature summary for 1.8.5.8 extracted from

  • Landry, A.P.; Moon, S.; Kim, H.; Yadav, P.K.; Guha, A.; Cho, U.S.; Banerjee, R.
    A catalytic trisulfide in human sulfide quinone oxidoreductase catalyzes coenzyme A persulfide synthesis and inhibits butyrate oxidation (2019), Cell Chem. Biol., 26, 1515-1525.e4 .
    View publication on PubMedView publication on EuropePMC

Crystallization (Commentary)

Crystallization (Comment) Organism
purified SQR in the absence and presence of CoQ1, a soluble CoQ10 analogue, and with/without sulfite or sulfide, X-ray diffraction structure determination and analysis at 2.0-2.8 A resolution. Soaking SQR-CoQ1 crystals with sodium sulfide provided evidence for in crystallo catalysis and captures CoQ1 exiting a long hydrophobic channel leading from FAD to the putative membrane-facing surface of SQR Homo sapiens

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
additional information Michaelis-Menten analysis of SQR activity at varying CoA concentrations. Pre-steady state kinetic analysis of ndSQR-mediated sulfur transfer to CoA Homo sapiens

Localization

Localization Comment Organism GeneOntology No. Textmining
mitochondrion
-
Homo sapiens 5739
-

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
hydrogen sulfide + glutathione + quinone Homo sapiens
-
S-sulfanylglutathione + quinol
-
?

Organism

Organism UniProt Comment Textmining
Homo sapiens Q9Y6N5
-
-

Reaction

Reaction Comment Organism Reaction ID
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 Homo sapiens

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
hydrogen sulfide + CoA + coenzyme Q1
-
Homo sapiens CoA-SSH + H+ + reduced coenzyme Q1
-
?
hydrogen sulfide + glutathione + coenzyme Q1
-
Homo sapiens glutathione persulfide + H+ + reduced coenzyme Q1
-
?
hydrogen sulfide + glutathione + decylubiquinone
-
Homo sapiens S-sulfanylglutathione + decylubiquinol
-
?
hydrogen sulfide + glutathione + quinone
-
Homo sapiens S-sulfanylglutathione + quinol
-
?
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 Homo sapiens ?
-
-

Synonyms

Synonyms Comment Organism
SQR
-
Homo sapiens
sulfide quinone oxidoreductase
-
Homo sapiens

Cofactor

Cofactor Comment Organism Structure
coenzyme Q10 CoQ10 Homo sapiens
decylubiquinone
-
Homo sapiens
FAD required Homo sapiens

General Information

General Information Comment Organism
additional information the large cavity extending from the matrix face to the active site exposes Cys379 and explains the vulnerability of solubilized SQR to errant attack by nucleophiles (sulfite, GSH, homocysteine, cysteine and methanethiol). Docking models reveal that either GSH or CoA can be accommodated at the mouth of the cavity with their thiol moieties oriented to interact with the 379Cys-SSH intermediate. The significantly greater intracellular concentration of GSH than sulfite or methanethiol, except perhaps under pathological conditions, is predicted to favor GSSH formation. Overall structure and active site architecture of SQR, overview. The sulfur substrate entry site is on the matrix side, CoQ entry from the mitochondrial membrane side Homo sapiens
physiological function the catalytic promiscuity of human sulfide quinone oxidoreductase supports formation of CoA-persulfide, a known inhibitor of short-chain fatty acid oxidation in colonocytes, analysis of several enzyme crystal structures shows a different mechanism for sulfide oxidation, which is catalyzed by an active site cysteine trisulfide. Identification of CoA as an additional sulfur acceptor for human SQR, its generation in situ leads to formation of the inhibitory CoA-SS- to FAD charge-transfer complex in human ACADS (short-chain specific acyl-CoA dehydrogenase) Homo sapiens