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Title: | Acidity of persulfides and its modulation by the protein environments in sulfide quinone oxidoreductase and thiosulfate sulfurtransferase. |
Authors: | Benchoam, Dayana Cuevasanta, Ernesto Roman, Joseph V. Banerjee, Ruma Alvarez, Beatriz |
Type: | Artículo |
Descriptors: | PERSULFUROS, SULFURO DE HIDROGENO, EFECTO ALFA, TIOL, SULFURO, QUINONA OXIDORREDUCTASA, TIOSULFATO, AZUFRETRANSFERASA, RODANASA |
Issue Date: | 2024 |
Abstract: | Persulfides (RSSH/RSS−) participate in sulfur metabolism
and are proposed to transduce hydrogen sulfide (H2S)
signaling. Their biochemical properties are poorly understood.
Herein, we studied the acidity and nucleophilicity of several
low molecular weight persulfides using the alkylating agent,
monobromobimane. The different persulfides presented
similar pKa values (4.6–6.3) and pH-independent rate constants
(3.2–9.0 × 103 M−1 s−1), indicating that the substituents in
persulfides affect properties to a lesser extent than in thiols
because of the larger distance to the outer sulfur. The persulfides
had higher reactivity with monobromobimane than
analogous thiols and putative thiols with the same pKa,
providing evidence for the alpha effect (enhanced nucleophilicity
by the presence of a contiguous atom with high electron
density). Additionally, we investigated two enzymes from the
human mitochondrial H2S oxidation pathway that form catalytic
persulfide intermediates, sulfide quinone oxidoreductase
and thiosulfate sulfurtransferase (TST, rhodanese). The pH
dependence of the activities of both enzymes was measured
using sulfite and/or cyanide as sulfur acceptors. The TST halfreactions
were also studied by stopped-flow fluorescence
spectroscopy. Both persulfidated enzymes relied on protonated
groups for reaction with the acceptors. Persulfidated sulfide
quinone oxidoreductase appeared to have a pKa of 7.8 ± 0.2.
Persulfidated TST presented a pKa of 9.38 ± 0.04, probably due
to a critical active site residue rather than the persulfide itself.
The TST thiol reacted in the anionic state with thiosulfate,
with an apparent pKa of 6.5 ± 0.1. Overall, our study contributes
to a fundamental understanding of persulfide properties and
their modulation by protein environments. |
Publisher: | American Society for Biochemistry and Molecular Biology |
IN: | Journal of Biological Chemistry, v. 300, nº 5, 2024 -- e107149 |
Citation: | Benchoam, D, Cuevasanta, E y otros. Acidity of persulfides and its modulation by the protein environments in sulfide quinone oxidoreductase and thiosulfate sulfurtransferase. Journal of Biological Chemistry [en línea], v. 300, nº 5, 2024. -- e107149. 14 p. |
Appears in Collections: | Publicaciones académicas y científicas - Facultad de Química |
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