IUBMB Enzyme Nomenclature


Accepted name: thyroxine 5-deiodinase

Reaction: 3,3',5'-triiodo-L-thyronine + iodide + acceptor + H+ = L-thyroxine + reduced acceptor

Other name(s): diiodothyronine 5'-deiodinase (ambiguous); iodothyronine 5-deiodinase; iodothyronine inner ring monodeiodinase; type III iodothyronine deiodinase

Systematic name: 3,3',5'-triiodo-L-thyronine,iodide:acceptor oxidoreductase (iodinating)

Comments: The enzyme activity has only been demonstrated in the direction of 5-deiodination. This removal of the 5-iodine, i.e. from the inner ring, largely inactivates the hormone thyroxine.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


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. Körhle, J. Iodothyronine deiodinases. Methods Enzymol. 347 (2002) 125-167. [PMID: 11898402]

[EC created 2003 as EC, transferred 2015 to EC]

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