Bacterial and mammalian thioredoxin systems activate iodothyronine 5'-deiodination |
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Authors: | A K Das B C Hummel F K Gleason A Holmgren P G Walfish |
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Institution: | Thyroid Research Laboratory, Mount Sinai Hospital, Toronto, Ont., Canada. |
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Abstract: | The identity of a dithiol (designated DFB) of relative mass (Mr) = 13,000, reported previously to be present in fraction B of rat liver cytosol and to participate as a cofactor in the 5'-deiodination of iodothyronines, has been investigated. Substitution of highly purified thioredoxin from Escherichia coli for fraction B or of highly purified thioredoxin reductase from either E. coli or rat liver for cytosolic fraction A (containing DFB reductase) permits deiodination of 3,3',5'-125I]triiodothyronine by rat liver microsomes to proceed. Addition of antibodies to highly purified rat-liver thioredoxin or thioredoxin reductase inhibits deiodination. Thus, the thioredoxin system largely accounts for the activity of the cytosolic cofactor system supporting 5'-deiodination of 3,3',5'-triiodothyronine in rat liver. |
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