Human mitochondrial persulfide dioxygenase is potently and reversibly inhibited by nitric oxide

Hydrogen sulfide (H 2 S) regulates multiple human physiological processes, its reactivity and range of action being tightly controlled through regulation of H 2 S-synthesizing and -detoxifying enzymes. H 2 S detoxification is mainly achieved by a mitochondrial sulfide detoxifying pathway including persulfide dioxygenase (PDO). Human PDO (known as ethylmalonic encephalopathy protein 1, ETHE1), a homodimeric enzyme with a mononuclear iron centre active site, catalyzes the conversion of glutathione persulfide (GSSH) and O 2 to reduced glutathione (GSH) and sulfite. Here we report that ETHE1 is potently inhibited by authentic nitric oxide (NO) gas at physiological concentrations, as observed by high resolution respirometry. Inhibition is reversible, occurs via NO binding to the reduced mononuclear iron center and becomes more potent and persistent at lower O 2 levels. Incubation with s -nitrosoglutathione (GSNO) also appears to partially and transiently inhibit ETHE1, this effect likely resulting from s -nitrosation of cysteine residues. While ETHE1 is devoid of NO reductase activity, in aerobic conditions it displays low NO degrading activity. These findings unravel a novel layer of cross-regulation between the H 2 S and NO gasotransmitters with possible implications on the regulation of numerous physiological and pathophysiological processes. • ETHE1 is potently and reversibly inhibited by authentic nitric oxide (NO) gas at physiological concentrations. • Incubation with s -nitrosoglutathione (GSNO) transiently inhibits ETHE1 likely via cysteine s -nitrosation. • Control of ETHE1 activity by NO and nitrosothiols constitutes another regulatory mechanism for mitochondrial hydrogen sulfide detoxification. • ETHE1 slowly degrades NO in aerobic but not in anaerobic conditions.