Demethylation of Methylmercury in Bird, Fish, and Earthworm

Alain Manceau (1) , Jean-Paul Bourdineaud (2) , Ricardo Oliveira (3) , Sandra L.F. Sarrazin (3) , David Krabbenhoft (4) , Collin Eagles-Smith (4) , Joshua Ackerman (4) , A. Robin Stewart (4) , Christian Ward-Deitrich (5) , M. Estela del Castillo Busto (5) , Heidi Goenaga-Infante (5) , Aude Wack (1) , Marius Retegan (6) , Blanka Detlefs (6) , Pieter Glatzel (6) , Paco Bustamante (7, 8) , Kathryn Nagy (9) , Brett Poulin (4, 10)

1 ISTerre - Institut des Sciences de la Terre
2 IECB - Imagerie Moléculaire et Nanobiotechnologies - Institut Européen de Chimie et Biologie
3 UFOPA - Universidade Federal do Oeste do Pará [Santarém]
4 USGS - United States Geological Survey
5 LGC Limited
6 ESRF - European Synchrotron Radiation Facility
7 LIENSs - LIttoral ENvironnement et Sociétés
8 IUF - Institut universitaire de France
9 University of Illinois at Chicago
10 UC Davis - University of California [Davis]

Toxicity of methylmercury (MeHg) to wildlife and humans results from its binding to cysteine residues of proteins, forming MeHg-cysteinate (MeHgCys) complexes that hinder biological functions. MeHgCys complexes can be detoxified in vivo, yet how this occurs is unknown. We report that MeHgCys complexes are transformed into selenocysteinate [Hg(Sec)4] complexes in multiple animals from two phyla (a waterbird, freshwater fish, and earthworms) sampled in different geographical areas and contaminated by different Hg sources. In addition, high energy-resolution X-ray absorption spectroscopy (HR-XANES) and chromatography-inductively coupled plasma mass spectrometry of the waterbird liver support the binding of Hg(Sec)4 to selenoprotein P and biomineralization of Hg(Sec)4 to chemically inert nanoparticulate mercury selenide (HgSe). The results provide a foundation for understanding mercury detoxification in higher organisms and suggest that the identified MeHgCys to Hg(Sec)4 demethylation pathway is common in nature.

Mots clés: Mercury; selenocysteine; selenoprotein P; speciation; HR-XANES; HR-EXAFS; HPLC-ICPMS

Domaines: Chimie

Alain Manceau, Jean-Paul Bourdineaud, Ricardo Oliveira, Sandra L.F. Sarrazin, David Krabbenhoft, et al.. Demethylation of Methylmercury in Bird, Fish, and Earthworm. Environmental Science and Technology, 2021, 55 (3), pp.1527-1534. ⟨10.1021/acs.est.0c04948⟩. ⟨hal-03144112⟩