Sulfide:quinone oxidoreductase (SQOR) (SQOR)

Sulfide:quinone oxidoreductase (SQOR) is a nuclear-encoded mitochondrial enzyme essential for the detoxification and signaling of hydrogen sulfide (H2S) (UniProt P24340). It catalyzes the first and rate-limiting step of H2S oxidation, transferring electrons from H2S to the ubiquinone pool in the mitochondrial respiratory chain (Libiad et al., 2014, J. Biol. Chem.). This process prevents the toxic accumulation of H2S, which is a potent inhibitor of cytochrome c oxidase (Complex IV) (Friederich et al., 2017, Am. J. Hum. Genet.). Mutations in the SQOR gene or alterations in its mRNA expression are linked to severe mitochondrial disorders, including Leigh-like syndrome and episodic metabolic acidosis (Friederich et al., 2017). Beyond its role in detoxification, SQOR-mediated H2S metabolism is involved in regulating redox homeostasis and cellular signaling, making it a potential therapeutic target in cancer and inflammatory diseases (Landry et al., 2021, Antioxid. Redox Signal.). While no FDA-approved drugs currently target SQOR mRNA or the protein, experimental inhibitors and mRNA-based approaches are being investigated to modulate H2S levels for therapeutic benefit (Jackson et al., 2012, Methods Enzymol.).

Other names

SQRSQRDLSulfide:quinone reductase-like (mitochondrial)Sulfide:quinone oxidoreductase, mitochondrialPRO1975

Oxidation of hydrogen sulfide to persulfides with concomitant reduction of ubiquinone to ubiquinol