Protein polysulfidation-dependent persulfide dioxygenase activity of ethylmalonic encephalopathy protein 1.

Reactive persulfide species such as glutathione persulfide (GSSH) are highly abundant biomolecules. Persulfide dioxygenase (also called ethylmalonic encephalopathy protein 1, ETHE1) reportedly metabolizes GSSH to GSH with simultaneous oxygen consumption. How ETHE1 activity is regulated is still unclear, however. In this study, we describe the possible role of protein polysulfidation in the catalytic activity of ETHE1. We first found that ETHE1 catalyzed the persulfide dioxygenase reaction mostly for glutathione polysulfides, GS-(S)-H, as well as for GSSH, but not for other endogenous persulfides such as cysteine and homocysteine persulfides/polysulfides. We then developed a novel method to detect protein polysulfidation and named it the polyethylene glycol-conjugated maleimide-labeling gel shift assay (PMSA). PMSA analysis indicated that most cysteine residues in ETHE1 were polysulfidated. Site-directed mutagenesis of cysteine residues in ETHE1 combined with liquid chromatography tandem mass spectrometry for polysulfidation determination surprisingly indicated that the Cys247 residue was important for polysulfidation of other Cys residues and that the C247S mutant possessed no persulfide dioxygenase activity. These results suggested that ETHE1 is a major enzyme regulating endogenous GSSH/GS-(S)-H and that its activity is controlled by polysulfidation of the Cys247 residue.