Species-specific differences in the inhibition of human and zebrafish 11beta-hydroxysteroid dehydrogenase 2 by thiram and organotins
- Authors
- Meyer, A., Strajhar, P., Murer, C., Da Cunha, T., and Odermatt, A.
- ID
- ZDB-PUB-120718-33
- Date
- 2012
- Source
- Toxicology 301(1-3): 72-78 (Journal)
- Registered Authors
- Keywords
- dithiocarbamate, thiram, organotin, cadmium, 11β-hydroxysteroid
- MeSH Terms
-
- Animals
- 11-beta-Hydroxysteroid Dehydrogenase Type 2/antagonists & inhibitors*
- 11-beta-Hydroxysteroid Dehydrogenase Type 2/chemistry
- 11-beta-Hydroxysteroid Dehydrogenase Type 2/metabolism
- Thiram/toxicity*
- Humans
- Mice
- Zebrafish
- Organotin Compounds/toxicity*
- HEK293 Cells
- Amino Acid Sequence
- Species Specificity
- Amino Acid Substitution
- PubMed
- 22796344 Full text @ Toxicology
- CTD
- 22796344
Dithiocarbamates and organotins can inhibit enzymes by interacting with functionally essential sulfhydryl groups. Both classes of chemicals were shown to inhibit human 11β-hydroxysteroid dehydrogenase 2 (11β-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, 11β-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 11β-HSD2 activity of the model species zebrafish. A comparison with human and mouse 11β-HSD2 revealed species-specific substrate preference. Unexpectedly, assessment of the effects of thiram and several organotins on the activity of zebrafish 11β-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 11β-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 ten-fold increased sensitivity of zebrafish 11β-HSD2 to thiram. Mutating cysteine-264 on human 11β-HSD2 to serine resulted in 100-fold lower inhibitory activity. Our results demonstrate significant species differences in the sensitivity of human and zebrafish 11β-HSD2 to inhibition by thiram and organotins. Site-directed mutagenesis revealed a key role of cysteine-264 in the substrate binding pocket of human 11β-HSD2 for sensitivity to sulfhydryl modifying agents.