title: Thyroxine 5'-deiodinase activity in brown adipose tissue.
abstract: Homogenates of rat brown adipose tissue (BAT) and epididymal fat pad (EPI) catalyze the 5'-deiodination of 3,3',5'-triiodothyronine (rT3) in the presence of dithiothreitol. BAT, but not EPI, catalyzes the 5'-deiodination of thyroxinE (T4) generating equal amounts of 3,5,3'-triiodothyronine (T3) and iodide. BAT 5'-deiodinase activity was unaffected by propylthiouracil (PTU) and was elevated in hypothyroid rats, whereas EPI 5'-deiodinase was totally inhibited by PTU and was depressed in hypothyroidism. These results indicate that type II (PTU-insensitive) 5'-iodothyronine deiodinase activity is present in BAT.
mesh_terms: D000273:Adipose Tissue / Q000201:enzymology; D002001:Adipose Tissue, Brown / Q000201:enzymology*; D000818:Animals; D007453:Iodide Peroxidase / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009928:Organ Specificity; D010544:Peroxidases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013965:Thyroidectomy
chemical_list: D010544:Peroxidases; D007453:Iodide Peroxidase