Journal
TOXICOLOGY
Volume 301, Issue 1-3, Pages 72-78Publisher
ELSEVIER IRELAND LTD
DOI: 10.1016/j.tox.2012.07.001
Keywords
Dithiocarbamate; Thiram; Organotin; Cadmium; 11 beta-Hydroxysteroid dehydrogenase; Glucocorticoid
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Funding
- Swiss National Science Foundation [PDFMP3_127330]
- Swiss National Science Foundation (SNF) [PDFMP3_127330] Funding Source: Swiss National Science Foundation (SNF)
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Dithiocarbamates and organotins can inhibit enzymes by interacting with functionally essential sulfhydryl groups. Both classes of chemicals were shown to inhibit human 11 beta-hydroxysteroid dehydrogenase 2 (11 beta-HSD2), which converts active cortisol into inactive cortisone and has a role in renal and intestinal electrolyte regulation and in the feto-placental barrier to maternal glucocorticoids. In fish, 11 beta-HSD2 has a dual role by inactivating glucocorticoids and generating the major androgen 11-ketotestosterone. Inhibition of this enzyme may enhance glucocorticoid and diminish androgen effects in fish. Here, we characterized 11 beta-HSD2 activity of the model species zebrafish. A comparison with human and mouse 11 beta-HSD2 revealed species-specific substrate preference. Unexpectedly, assessment of the effects of thiram and several organotins on the activity of zebrafish 11 beta-HSD2 showed weak inhibition by thiram and no inhibition by any of the organotins tested. Sequence comparison revealed the presence of an alanine at position 253 on zebrafish 11 beta-HSD2, corresponding to cysteine-264 in the substrate-binding pocket of the human enzyme. Substitution of alanine-253 by cysteine resulted in a more than 10-fold increased sensitivity of zebrafish 11 beta-HSD2 to thiram. Mutating cysteine-264 on human 11 beta-HSD2 to serine resulted in 100-fold lower inhibitory activity. Our results demonstrate significant species differences in the sensitivity of human and zebrafish 11 beta-HSD2 to inhibition by thiram and organotins. Site-directed mutagenesis revealed a key role of cysteine-264 in the substrate-binding pocket of human 11 beta-HSD2 for sensitivity to sulfhydryl modifying agents. (c) 2012 Elsevier Ireland Ltd. All rights reserved.
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