title: Reaction of the type III iodothyronine deiodinase with the affinity label N-bromoacetyl-triiodothyronine.
abstract: The type III iodothyronine deiodinase (ID-III) catalyzes the inner ring deiodination and, thus, the inactivation of the thyroid hormones T4 and T3. ID-III activity in rat brain, rat placenta and embryonic chicken liver is inhibited by the affinity label N-bromoacetyl-T3 (BrAcT3) with an affinity similar to that of T3. Reaction of rat brain and placenta microsomes with BrAc[125I]T3 resulted in the extensive labeling of a 32 kDa protein (p32). However, p32 was also prominently labeled in fetal rat liver microsomes which have no ID-III activity. Labeling of p32 was not influenced by 100 microM substrate analogs or inhibitors of ID-III, some of which completely inhibit ID-III activity at 1 microM. BrAc[125I]T3 labeling of embryonic chicken liver microsomes did not reveal p32 or another protein possibly related to ID-III. In contrast to previous suggestions, it is unlikely that p32 represents ID-III or a subunit thereof.
authors.affiliation: Department of Internal Medicine III, Erasmus University Medical School, Rotterdam, The Netherlands.
authors.forename: C H
authors.initials: CH
authors.lastname: Schoenmakers
authors.forename: I G
authors.initials: IG
authors.lastname: Pigmans
authors.forename: E
authors.initials: E
authors.lastname: Kaptein
authors.forename: V M
authors.initials: VM
authors.lastname: Darras
authors.forename: T J
authors.initials: TJ
authors.lastname: Visser
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001921:Brain / Q000196:embryology / Q000201:enzymology; D002642:Chick Embryo; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D008297:Male; D008861:Microsomes / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology; D010920:Placenta / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D014284:Triiodothyronine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D000345:Affinity Labels; D014284:Triiodothyronine; C036219:N-bromoacetyl-3,3',5-triiodothyronine; D007453:Iodide Peroxidase