Click here to close Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly. We suggest using a current version of Chrome, FireFox, or Safari.
XB-ART-20938
Proc Natl Acad Sci U S A 1994 Aug 02;9116:7767-71.
Show Gene links Show Anatomy links

A thyroid hormone-regulated gene in Xenopus laevis encodes a type III iodothyronine 5-deiodinase.

St Germain DL , Schwartzman RA , Croteau W , Kanamori A , Wang Z , Brown DD , Galton VA .


???displayArticle.abstract???
The type III iodothyronine 5-deiodinase metabolizes thyroxine and 3,5,3'-triiodothyronine to inactive metabolites by catalyzing the removal of iodine from the inner ring. The enzyme is expressed in a tissue-specific pattern during particular stages of development in amphibia, birds, and mammals. Recently, a PCR-based subtractive hybridization technique has been used to isolate cDNAs prepared from Xenopus laevis tadpole tail mRNA that represent genes upregulated by thyroid hormone during metamorphosis. Sequence analysis of one of these cDNAs (XL-15) revealed regions of homology to the mRNA encoding the rat type I (outer ring) 5'-deiodinase, including a conserved UGA codon that encodes selenocysteine in the mammalian enzyme. We report here that the protein encoded by the XL-15 cDNA efficiently catalyzes the (inner ring) 5-deiodination of 3,5,3'-triiodothyronine with a Km value of 2 nM and is resistant to inhibition by propylthiouracil and aurothioglucose. Our analysis confirms that the UGA codon encodes a selenocysteine that is critical for the catalytic activity of the enzyme. In addition, the direct induction of XL-15 mRNA levels by thyroid hormone in X. laevis tadpole tail tissue and cultured cell lines correlates closely with increases in 5- (but not 5'-) deiodinase activity. These findings indicate that the XL-15 cDNA encodes a type III 5-deiodinase and underscores the importance of the trace element selenium in thyroid hormone metabolism.

???displayArticle.pubmedLink??? 8052658
???displayArticle.pmcLink??? PMC44483
???displayArticle.link??? Proc Natl Acad Sci U S A


Species referenced: Xenopus laevis
Genes referenced: dio2

References [+] :
Berry, Type I iodothyronine deiodinase is a selenocysteine-containing enzyme. 1991, Pubmed, Xenbase