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ENZYME entry: EC 1.21.99.4

Accepted Name
Thyroxine 5'-deiodinase.
Alternative Name(s)
Diiodothyronine 5'-deiodinase.
Iodothyronine 5'-deiodinase.
Iodothyronine outer ring monodeiodinase.
L-thyroxine iodohydrolase (reducing).
Thyroxine 5-deiodinase.
Type I iodothyronine deiodinase.
Type II iodothyronine deiodinase.
Reaction catalysed
3,5,3'-triiodo-L-thyronine + iodide + A + H(+) <=> L-thyroxine + AH(2)
Comment(s)
  • 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.
  • Formerly EC 1.97.1.10 and EC 3.8.1.4.
Cross-references
PROSITEPDOC00172 ; PDOC00925
BRENDA1.21.99.4
EC2PDB1.21.99.4
ExplorEnz1.21.99.4
PRIAM enzyme-specific profiles1.21.99.4
KEGG Ligand Database for Enzyme Nomenclature1.21.99.4
IUBMB Enzyme Nomenclature1.21.99.4
IntEnz1.21.99.4
MEDLINEFind literature relating to 1.21.99.4
MetaCyc1.21.99.4
UniProtKB/Swiss-Prot
P49894, IOD1_CANLF;  O42411, IOD1_CHICK;  Q6V915, IOD1_FELCA;  
Q804E1, IOD1_FUNHE;  P49895, IOD1_HUMAN;  Q61153, IOD1_MOUSE;  
O42449, IOD1_ORENI;  Q6QN13, IOD1_PIG;  A4GT88, IOD1_RABIT;  
P24389, IOD1_RAT;  Q95N00, IOD1_SUNMU;  Q2QEI3, IOD1_XENLA;  
Q5I3B2, IOD2_BOVIN;  Q9IAX2, IOD2_CHICK;  P79747, IOD2_FUNHE;  
Q92813, IOD2_HUMAN;  P49896, IOD2_LITCT;  Q9Z1Y9, IOD2_MOUSE;  
Q8UVX8, IOD2_NEOFS;  L7WGA7, IOD2_PETMA;  Q6QN12, IOD2_PIG;  
P70551, IOD2_RAT;  Q6U6H1, IOD_HALRO;  

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