Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.14/175932
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- Title
- New insights into the metabolism of organomercury compounds : mercury-containing cysteine S-conjugates are substrates of human glutamine transaminase K and potent inactivators of cystathionine γ-lyase
- Related
- Archives of biochemistry and biophysics, Vol. 517, No. 1, (2012), p.20-29
- DOI
- 10.1016/j.abb.2011.11.002
- Publisher
- Elsevier
- Date
- 2012
- Author/Creator
- Bridges, Christy C
- Author/Creator
- Krasnikov, Boris F
- Author/Creator
- Joshee, Lucy
- Author/Creator
- Pinto, John T
- Author/Creator
- Hallen, André
- Author/Creator
- Li, Jianyong
- Author/Creator
- Zalups, Rudolfs K
- Author/Creator
- Cooper, Arthur J. L
- Description
- Anthropogenic practices and recycling in the environment through natural processes result in release of potentially harmful levels of mercury into the biosphere. Mercury, especially organic forms, accumulates in the food chain. Mercury reacts readily with sulfur-containing compounds and often exists as a thiol S-conjugate, such as the l-cysteine (Cys)-S-conjugate of methylmercury (CH₃Hg-S-Cys) or inorganic mercury (Cys-S-Hg-S-Cys). These S-conjugates are structurally similar to l-methionine and l-cystine/l-cystathionine, respectively. Bovine and rat glutamine transaminase K (GTK) catalyze transamination of sulfur-containing amino acids. Recombinant human GTK (rhGTK) has a relatively open catalytic active site, and we report here that this enzyme, like the rat and bovine enzymes, can also utilize sulfur-containing l-amino acids, including l-methionine, l-cystine, and l-cystathionine as substrates. The current study extends this list to include mercuric S-conjugates, and shows that CH₃Hg-S-Cys and Cys-S-Hg-S-Cys are substrates and reversible inhibitors of rhGTK. The homocysteine S-conjugates, Hcy-S-Hg-S-Hcy and CH₃Hg-S-Hcy, are also inhibitors. Finally, we show that HgCl₂, CH₃Hg-S-Cys and Cys-S-Hg-S-Cys are potent irreversible inhibitors of rat cystathionine γ-lyase. The present study broadens our knowledge of the biochemistry of mercury compounds by showing that Cys S-conjugates of mercury interact with enzymes that catalyze transformations of biologically important sulfur-containing amino acids.
- Description
- 10 page(s)
- Subject Keyword
- Cystathionine γ-lyase
- Subject Keyword
- Glutamine transaminase K
- Subject Keyword
- Kynurenine aminotransferase isozyme I
- Subject Keyword
- Mercury cysteine S-conjugate
- Subject Keyword
- Methylmercury cysteine S-conjugate
- Subject Keyword
- Sulfur-containing amino acids
- Resource Type
- journal article
- Organisation
- Macquarie University. Dept. of Chemistry and Biomolecular Sciences
- Identifier
- http://hdl.handle.net/1959.14/175932
- Identifier
- ISSN:0003-9861
- Identifier
- mq_res-ext-2-s2.0-84155172720
- Language
- eng
- Reviewed
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