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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 J+Biol+Chem
2015 ; 290
(13
): 8310-20
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Sulfide oxidation by a noncanonical pathway in red blood cells generates
thiosulfate and polysulfides
#MMPMID25688092
Vitvitsky V
; Yadav PK
; Kurthen A
; Banerjee R
J Biol Chem
2015[Mar]; 290
(13
): 8310-20
PMID25688092
show ga
A cardioprotectant at low concentrations, H2S is a toxin at high concentrations
and inhibits cytochrome c oxidase. A conundrum in H2S homeostasis is its fate in
red blood cells (RBCs), which produce H2S but lack the canonical mitochondrial
sulfide oxidation pathway for its clearance. The sheer abundance of RBCs in
circulation enhances the metabolic significance of their clearance strategy for
H2S, necessary to avoid systemic toxicity. In this study, we demonstrate that H2S
generation by RBCs is catalyzed by mercaptopyruvate sulfurtransferase.
Furthermore, we have discovered the locus of sulfide oxidation in RBCs and
describe a new role for an old protein, hemoglobin, which in the ferric or
methemoglobin state binds H2S and oxidizes it to a mixture of thiosulfate and
hydropolysulfides. Our study reveals a previously undescribed route for the
biogenesis of hydropolysulfides, which are increasingly considered important for
H2S-based signaling, but their origin in mammalian cells is unknown. An
NADPH/flavoprotein oxidoreductase system restores polysulfide-carrying hemoglobin
derivatives to ferrous hemoglobin, thus completing the methemoglobin-dependent
sulfide oxidation cycle. Methemoglobin-dependent sulfide oxidation in mammals is
complex and has similarities to chemistry reported for the dissolution of iron
oxides in sulfidic waters and during bioleaching of metal sulfides. The catalytic
oxidation of H2S by hemoglobin explains how RBCs maintain low steady-state H2S
levels in circulation, and suggests that additional hemeproteins might be
involved in sulfide homeostasis in other tissues.