The Enzyme Database

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Accepted name: thyroxine 5′-deiodinase
Reaction: 3,5,3′-triiodo-L-thyronine + iodide + A + H+ = L-thyroxine + AH2
Other name(s): diiodothyronine 5′-deiodinase [ambiguous]; iodothyronine 5′-deiodinase; iodothyronine outer ring monodeiodinase; type I iodothyronine deiodinase; type II iodothyronine deiodinase; thyroxine 5-deiodinase [misleading]; L-thyroxine iodohydrolase (reducing)
Systematic name: acceptor:3,5,3′-triiodo-L-thyronine oxidoreductase (iodinating)
Comments: The enzyme activity has only been demonstrated in the direction of 5′-deiodination, which renders the thyroid hormone more active. The enzyme consists of type I and type II enzymes, both containing selenocysteine, but with different kinetics. For the type I enzyme the first reaction is a reductive deiodination converting the -Se-H group of the enzyme into an -Se-I group; the reductant then reconverts this into -Se-H, releasing iodide.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 70712-46-8
1.  Chopra, I.J. and Teco, G.N.C. Characteristics of inner ring (3 or 5) monodeiodination of 3,5-diiodothyronine in rat liver: evidence suggesting marked similarities of inner and outer ring deiodinases for iodothyronines. Endocrinology 110 (1982) 89–97. [PMID: 7053997]
2.  Goswani, A., Leonard, J.L. and Rosenberg, I.N. Inhibition by coumadin anticoagulants of enzymatic outer ring monodeiodination of iodothyronines. Biochem. Biophys. Res. Commun. 104 (1982) 1231–1238. [PMID: 6176242]
3.  Smallridge, R.C., Burman, K.D., Ward, K.E., Wartofsky, L., Dimond, R.C., Wright, F.D. and Lathan, K.R. 3′,5′-Diiodothyronine to 3′-monoiodothyronine conversion in the fed and fasted rat: enzyme characteristics and evidence for two distinct 5′-deiodinases. Endocrinology 108 (1981) 2336–2345. [PMID: 7227308]
4.  Körhle, J. Iodothyronine deiodinases. Methods Enzymol. 347 (2002) 125–167. [PMID: 11898402]
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