EC Explorer
[browse EC tree] - [search]
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
back to topEC Tree
1 Oxidoreductases
1.1 Acting on the CH-OH group of donors
1.6.2.1 created 1961, deleted 1965 1.6.2.3 created 1972, deleted 1965 1.6.7.1 created 1972, deleted 1978 1.6.7.2 created 1972, deleted 1978 1.6.7.3 created 1978, deleted 1978
