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Reaction of the type III iodothyronine deiodinase with the affinity label N ‐bromoacetyl‐triiodothyronine
Author(s) -
Schoenmakers Christian H.H.,
Pigmans Ingrid G.A.J.,
Kaptein Ellen,
Darras Veerle M.,
Visser Theo J.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80449-5
Subject(s) - deiodinase , triiodothyronine , microsome , affinity labeling , iodothyronine deiodinase , biochemistry , protein subunit , affinity label , chemistry , placenta , medicine , enzyme , biology , endocrinology , hormone , fetus , gene , pregnancy , genetics
The type III iodothyronine deiodinase (ID‐III) catalyzes the inner ring deiodination and, thus, the inactivation of the thyroid hormones T 4 and T 3 . ID‐III activity in rat brain, rat placenta and embryonic chicken liver is inhibited by the affinity label N ‐bromoacetyl‐T 3 , (BrAcT 3 ) with an affinity similar to that of T 3 . Reaction of rat brain and placenta microsomes with BrAc[ 125 I]T 3 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 μM substrate analogs or inhibitors of ID‐III, some of which completely inhibit ID‐III activity at 1 μ. BrAc[ 125 I]T 3 , 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.