Important roles for hydrogen sulfide (H2S) in physiological and pathological function are emerging. H2S is the
fourth signaling gas molecule, following O2, NO and CO, that has been shown to be important for intra- and intermolecular
signal transduction. These gas molecules should bind to the heme iron complex and regulate numerous important
physiological functions such as transcription, guanylate cyclase, and phosphodiesterase. However, involvement of
heme proteins in H2S-regulated functions has not been critically considered. This paper is to sort out the complicated interactions
of H2S with heme proteins and to help advance our understanding of the molecular mechanism of the interaction
between H2S and heme proteins. Importantly, H2S interacts with the heme iron complex of myoglobin and hemoglobin
in the presence of H2O2, forming sulfheme (sulfur-incorporated porphyrin) iron complex with markedly different
physicochemical characters (such as oxygen binding affinity) in contrast to those of the normal heme iron complex. It is
suggested that involvement of the heme proteins in H2S-regulated physiological and pathological functions, in particular
under oxidative stress conditions, is much more crucial than generally thought.
Keywords: Heme protein, Hydrogen sulfide, Reactive oxygen species, Signal transduction, Sulfheme.
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