Abstract
Hydrogen sulfide (H2S/HS–) can be formed in mammalian tissues and exert physiological effects. It can react with metal centers and oxidized thiol products such as disulfides (RSSR) and sulfenic acids (RSOH). Reactions with oxidized thiol products form persulfides (RSSH/RSS–). Persulfides have been proposed to transduce the signaling effects of H2S through the modification of critical cysteines. They are more nucleophilic and acidic than thiols and, contrary to thiols, also possess electrophilic character. In this review, we summarize the biochemistry of hydrogen sulfide and persulfides, focusing on redox aspects. We describe biologically relevant one- and two-electron oxidants and their reactions with H2S and persulfides, as well as the fates of the oxidation products. The biological implications are discussed.
Highlights
Hydrogen sulfide (H2 S/HS– ) can be formed in mammalian tissues and exert physiological effects
Several reports assigned an antioxidant role for H2 S, which could be related to cytoprotective effects [21,22,23,24,25,26]; consideration of the kinetics of the reactions suggests that the protective role is not due to direct reactions of H2 S with oxidants, as will be described below [27]
Intermediate persulfides formed in the proteins mercaptopyruvate sulfurtransferase (MST), sulfide quinone oxidoreductase (SQR), and rhodanese can be transferred to several acceptors including cyanide, sulfite, and thiols [34,57,58,141,142,143,144]
Summary
Hydrogen sulfide (H2 S) is the simplest molecule containing reduced sulfur among the wide diversity of sulfur compounds It was first synthesized as a gas, and its composition was identified in the eighteenth century [1]. It is naturally occurring in geothermal sources [2] and has been related to the emergence and evolution of organisms in Earth [3]. It is a crucial molecule in the metabolism of several organisms, acting both as an electron donor in energetic pathways (anoxygenic photosynthesis and oxidative phosphorylation in lithotrophs [4]) and as a sulfur donor in synthetic pathways (cysteine and methionine synthesis, among others [5]). Several reports assigned an antioxidant role for H2 S, which could be related to cytoprotective effects [21,22,23,24,25,26]; consideration of the kinetics of the reactions suggests that the protective role is not due to direct reactions of H2 S with oxidants, as will be described below [27]
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