Different thyroid hormone‐deiodinating enzymes in tilapia (Oreochromis niloticus) liver and kidney
- 26 April 1993
- journal article
- research article
- Published by Wiley in FEBS Letters
- Vol. 321 (2-3), 140-144
- https://doi.org/10.1016/0014-5793(93)80095-c
Abstract
Enzymes catalyzing the outer ring deiodination (ORD) of iodothyronines are important for the regulation of thyroid hormone bioactivity. We have studied ORD of thyroxine (T4) and 3,3',5'-triiodothyronine (rT3) in liver and kidney microsomes offish, i.e. tilapia (Oreochromis niloticus). Tilapia kidney contains an enzyme which resembles the mammalian selenoenzyme type I iodothyronine deiodinase (ID-I) with respect to substrate preference (rT3 > T4) and high (≈ μM) K m values, but is much less sensitive to selenocysteine (Sec)-targeted inhibitors, including 6-propyl-2-thiouracil (PTU). In contrast, tilapia liver contains an enzyme very similar to mammalian type II deiodinase (ID-II) with respect to substrate preference (T4 > rT3), low (≈ nM) K m values, and lack of sensitivity to Sec inhibitors.Keywords
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