- Thyroid peroxidase
Name = thyroid peroxidase
HGNCid = 12015
Symbol = TPO
EntrezGene = 7173
OMIM = 606765
RefSeq = NM_175722
UniProt = P07202
ECnumber = 126.96.36.199
Chromosome = 2
LocusSupplementaryData = pter-p24
Thyroid peroxidase or Thyroperoxidase (TPO) is an
enzymemainly expressed in the thyroidthat liberates iodinefor addition onto tyrosineresidues on thyroglobulinfor the production of thyroxine(T4) or triiodothyronine(T3) ( thyroid hormones).
Inorganic iodine enters the body primarily as iodide, I-. After entering the
thyroid follicle(or thyroid follicular cell) via a Na+/I- symporter (NIS) on the basolateral side, iodide is shuttled across the apical membrane into the colloid via pendrin, after which thyroid peroxidase oxidizes iodide to atomic iodine (I) or iodinium (I+). The "organification of iodine," the incorporation of iodine to thyroglobulinfor the production of thyroid hormone is inseparable from oxidation and is catalyzed by TPO. The chemical reactions catalyzed by thyroid peroxidase occur on the outer apical membrane surface and are mediated by hydrogen peroxide.
timulation and inhibition
TPO is stimulated by
TSH, which upregulates gene expression. It is inhibited by the thioamidedrugs, such as propylthiouraciland methimazole.
It is a frequent
epitopeof autoantibodies in autoimmune thyroid disease (most commonly, Hashimoto's thyroiditis) so the antibody titercan be used to assess disease activity in patients who have developed such antibodies.
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