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EC 1.21.99.4 Details
show Brenda entryEC number
1.21.99.4
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 outer ring monodeiodinase,
type I iodothyronine deiodinase,
type II iodothyronine deiodinase,
thyroxine 5-deiodinase [misleading],
L-thyroxine iodohydrolase (reducing)
Systematic name
3,3′,5-triiodo-L-thyronine,iodide:acceptor oxidoreductase (iodinating)
CAS registry number
70712-46-8
Comment
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.
History
created 1984 as EC 3.8.1.4, transferred 2003 to EC 1.97.1.10, transferred 2015 to EC 1.21.99.4
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1 Oxidoreductases
1.1.1 With NAD+ or NADP+ as acceptor
1.1.3.1 created 1961, deleted 1984 1.1.3.25 created 1986, deleted 2005 1.1.3.26 created 1989, deleted 2002 1.1.3.31 created 1992, deleted 2003 1.1.3.32 created 1999, deleted 2002 1.1.3.33 created 1999, deleted 2002 1.1.3.34 created 1999, deleted 2002 1.1.3.35 created 1999, deleted 2002 1.1.3.36 created 1999, deleted 2002 1.1.99.15 created 1978, deleted 1980 1.1.99.17 created 1982, deleted 2003
