Thiosulfate dehydrogenases are bacterial cytochromes that contribute to the oxidation of inorganic sulfur. The active sites of these enzymes contain low-spin -type heme with Cys/His axial ligation. However, the reduction potentials of these hemes are several hundred mV more negative than that of the thiosulfate/tetrathionate couple (, +198 mV), making it difficult to rationalize the thiosulfate oxidizing capability. Here, we describe the reaction of thiosulfate dehydrogenase (TsdA) with sulfite, an analogue of thiosulfate. The reaction leads to stoichiometric conversion of the active site Cys to cysteinyl sulfonate (C-CH-S-SO) such that the protein exists in a form closely resembling a proposed intermediate in the pathway for thiosulfate oxidation that carries a cysteinyl thiosulfate (C-CH-S-SSO). The active site heme in the stable sulfonated protein displays an approximately 200 mV more positive than the Cys/His-ligated state. This can explain the thiosulfate oxidizing activity of the enzyme and allows us to propose a catalytic mechanism for thiosulfate oxidation. Substrate-driven release of the Cys heme ligand allows that side chain to provide the site of substrate binding and redox transformation; the neighboring heme then simply provides a site for electron relay to an appropriate partner. This chemistry is distinct from that displayed by the Cys-ligated hemes found in gas-sensing hemoproteins and in enzymes such as the cytochromes P450. Thus, a further class of thiolate-ligated hemes is proposed, as exemplified by the TsdA centers that have evolved to catalyze the controlled redox transformations of inorganic oxo anions of sulfur.

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9562282PMC
http://dx.doi.org/10.1021/jacs.2c06062DOI Listing

Publication Analysis

Top Keywords

reaction thiosulfate
8
thiosulfate dehydrogenase
8
heme ligand
8
thiosulfate
8
thiosulfate oxidizing
8
active site
8
thiosulfate oxidation
8
heme
5
dehydrogenase substrate
4
substrate mimic
4

Similar Publications

Harsh acid oxidation of activated charcoal transforms an insoluble carbon-rich source into water-soluble, disc structures of graphene decorated with multiple oxygen-containing functionalities. We term these pleiotropic nano-enzymes as "pleozymes". A broad redox potential spans many crucial redox reactions including the oxidation of hydrogen sulfide (HS) to polysulfides and thiosulfate, dismutation of the superoxide radical (O*), and oxidation of NADH to NAD.

View Article and Find Full Text PDF

Essential role of sulfide oxidation in brain health and neurological disorders.

Pharmacol Ther

December 2024

Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA. Electronic address:

Hydrogen sulfide (HS) is an environmental hazard well known for its neurotoxicity. In mammalian cells, HS is predominantly generated by transsulfuration pathway enzymes. In addition, HS produced by gut microbiome significantly contributes to the total sulfide burden in the body.

View Article and Find Full Text PDF

Long-isolated subsurface brine environments (Ma-Ga residence times) may be habitable if they sustainably provide substrates, e.g. through water-rock reactions, that support microbial catabolic energy yields exceeding maintenance costs.

View Article and Find Full Text PDF

Thin films of PbS, both undoped and cobalt-doped (Co-PbS), were produced on glass substrates using the straightforward and controllable approach of sequential ionic layer adsorption and reaction (SILAR). The reactive substances employed to deposit the PbS thin films were lead nitrate (Pb(NO)), cobalt nitrate (Co(NO₃)₂(H₂O)₆), sodium thiosulphate (NaSO) and HO for different dipping concentrations of lead and cobalt. The films were adherent to the substrate and were compact, and crack-free with a shiny silver color.

View Article and Find Full Text PDF

A contribution to the crystal chemistry and topology of organic thiosulfates: bis(1-methylpiperazinium)·SO·HO versus 1-methylpiperazinediium·SO·3HO.

Acta Crystallogr B Struct Sci Cryst Eng Mater

December 2024

Laboratory of Arctic Mineralogy and Material Sciences, Kola Science Centre, Russian Academy of Sciences, Apatity 184209, Russian Federation.

Single crystals of two new compounds, (CHN)SO·HO (1) and (CHN)SO·3HO (2), were isolated from the reaction products of 1-methylpiperazine, sulfuric acid, and barium thiosulfate in aqueous media. The crystal structures have been determined by single-crystal X-ray diffraction. In agreement to the previous observations, the organic template may contribute to the formation of thiosulfates both as mono- and diprotonated species, but this is the first case where both products are reported for the same organic compound.

View Article and Find Full Text PDF

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!