P66 Characterization of wild type and patient-described mutant forms of Human Persulfide Dioxygenase, ETHE1

Abstract

Hydrogen sulfide (H 2 S) is an endogenously produced gaseous signaling molecule with beneficial effects in various cellular processes in the central nervous system, cardiovascular system and gastrointestinal tract. The biogenesis of H 2 S involves the enzymes of the transsulfuration pathway cystathionine b-synthase and g-cystathionase. H 2 S oxidation and removal occurs in the mitochondria and the electrons from this oxidation are used in electron transfer chain to generate energy. Steady-state levels of H 2 S are controlled by its biogenesis in the transsulfuration pathway and its efficient oxygen-dependent catabolism in the mitochondria by a 3-enzyme pathway including sulfide quinone oxidoreductase, persulfide dioxygenase (ETHE1) and a sulfur transferase. Mutations in the persulfide dioxgenase, ETHE1, result in ethylmalonic encephalopathy, an inborn error of metabolism. In this study, we report the biochemical characterization and kinetic properties of human persulfide dioxygenase and describe the biochemical penalties associated with two patient mutations, T152I and D196N. Steady-state kinetic analysis reveals that the T152I mutation results in a 3-fold lower activity, which is correlated with a 3-fold lower iron content compared to the wild-type enzyme. The D196N mutation results in a 2-fold higher K M for the substrate, glutathione persulfide (GSSH).