Bacterial and mammalian thioredoxin systems activate iodothyronine 5'-deiodination.
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.
D000818:Animals; D001426:Bacterial Proteins / Q000502:physiology*; D002417:Cattle; D004789:Enzyme Activation; D004926:Escherichia coli; D008862:Microsomes, Liver / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000502:physiology*; D051381:Rats; D013880:Thioredoxin-Disulfide Reductase / Q000502:physiology*; D013879:Thioredoxins / Q000502:physiology*; D013970:Thyronines / Q000378:metabolism*
D001426:Bacterial Proteins; D013970:Thyronines; C019017:3'-monoiodothyronine; D013879:Thioredoxins; D009247:NADH, NADPH Oxidoreductases; D013880:Thioredoxin-Disulfide Reductase