Thyroid peroxidase
| iodide peroxidase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
ExPASy NiceZyme view | | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
| |||||||||
| thyroid peroxidase | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Symbol | TPO | ||||||
Chr. 2 pter-p24 | |||||||
| |||||||
Thyroid peroxidase, also called thyroperoxidase (TPO), thyroid specific peroxidase or iodide peroxidase, is an
thyroxine (T4) or triiodothyronine (T3), the thyroid hormones.[1] In humans, thyroperoxidase is encoded by the TPO gene.[2]
Catalyzed reaction
+ I− + H+ + H2O2 ⇒ 
+ 2 H2O
Iodide is oxidized to iodine radical which immediately reacts with tyrosine.
+ I− + H+ + H2O2 ⇒ 
+ 2 H2O
The second iodine atom is added in similar manner to the reaction intermediate 3-iodotyrosine.
Function
Thyroid hormone synthesis, with thyroid peroxidase performing the oxidation step seen at center-left in the image.[3]
Inorganic iodine enters the body primarily as iodide, I−. After entering the
oxidizes iodide to atomic iodine (I) or iodinium (I+). The "organification of iodine," the incorporation of iodine into thyroglobulin for the production of thyroid hormone, is nonspecific; that is, there is no TPO-bound intermediate, but iodination occurs via reactive iodine species released from TPO.[4]
The chemical reactions catalyzed by thyroid peroxidase occur on the outer apical membrane surface and are mediated by hydrogen peroxide.
Stimulation and inhibition
TPO is stimulated by TSH, which upregulates gene expression.
TPO is inhibited by the
methimazole.[5] In laboratory rats with insufficient iodine intake, genistein has demonstrated inhibition of TPO.[6]
Clinical significance
Thyroid peroxidase is a frequent
antibody titer can be used to assess disease activity in patients that have developed such antibodies.[7][8]
Diagnostic use
In diagnostic
papillary thyroid carcinoma.[9]
References
External links
- Thyroid+Peroxidase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
