SQOR (sulfide quinone oxidoreductase) is a mitochondrial inner membrane enzyme that catalyzes hydrogen sulfide oxidation using quinone cofactors, producing thiosulfate and sulfane atoms 1. The physiological electron acceptor is believed to be glutathione 23. SQOR functions as a key regulator of hydrogen sulfide (H2S) homeostasis and acts as a negative regulator of protein persulfidation 4. By oxidizing H2S, SQOR prevents its accumulation and maintains mitochondrial respiratory function during hypoxia 5. The enzyme also generates ubiquinol and hydropersulfides that provide antioxidant protection against ferroptosis 6. SQOR has emerging roles in multiple physiological processes. It regulates endothelial cell proliferation and angiogenesis; SQOR deficiency impairs hypoxic angiogenesis and limits tumor neovascularization 7. In macrophages, SQOR inhibition enhances protective S-persulfidation against oxidative-inflammatory stress 4. SQOR stability is controlled through ubiquitin-proteasome degradation pathways 89, affecting H2S levels and redox balance in tissues including testis 9. Clinically, SQOR dysfunction is associated with renal fibrosis pathogenesis 8, male infertility 9, and ischemic stroke 10. As a component of the sulfide oxidation unit, SQOR represents a therapeutic target for conditions involving hypoxia, oxidative stress, and ferroptosis-related diseases 115.