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Different thyroid hormone‐deiodinating enzymes in tilapia ( Oreochromis niloticus ) liver and kidney
Author(s) -
Mol Koen,
Kaptein Ellen,
Darras Veerle M.,
de Greef Wim J.,
Kühn Eduard R.,
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)80095-c
Subject(s) - deiodinase , tilapia , oreochromis , thyroid , medicine , enzyme , endocrinology , triiodothyronine , kidney , hormone , selenocysteine , chemistry , biology , biochemistry , cysteine , fish <actinopterygii> , fishery
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.