Triplets! Unexpected structural similarity among the three enzymes that catalyze initiation and termination of thyroid hormone effects.

Antonio C. Bianco

Research output: Contribution to journalReview article

4 Scopus citations


The three iodothyronine deiodinases catalyze the initiation (D1, D2) and termination (D3) of thyroid hormone effects in vertebrates. A recently conceived 3-dimensional model predicts that these enzymes share a similar structural organization and belong to the thioredoxin (TRX) fold superfamily. Their active center is a selenocysteine-containing pocket defined by the beta1-alpha1-beta2 motifs of the TRX fold and a domain that shares strong similarities with the active site of iduronidase, a member of the clan GH-A fold of glycoside hydrolases. While D1 and D3 are long-lived plasma membrane proteins, D2 is an endoplasmic reticulum resident protein with a half-life of only 20 min. D2 inactivation is mediated by selective UBC-7-mediated conjugation to ubiquitin, a process that is accelerated by T4 catalysis, thus maintaining local T3 homeostasis. In addition, D2 interacts with and is a substrate of the pVHL-interacting deubiquitinating enzymes (VDU1 and VDU2); thus deubiquitination regulates the supply of active thyroid hormone in D2-expressing cells.

Original languageEnglish (US)
Pages (from-to)16-24
Number of pages9
JournalArquivos brasileiros de endocrinologia e metabologia
Issue number1
StatePublished - Feb 2004


ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism

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