In the Thyroid peroxidase world, there are endless aspects that deserve to be explored and discussed. Whether Thyroid peroxidase is a person, a topic, a date or any other concept, its relevance and impact on our lives become evident as we delve deeper into its meaning and repercussions. From its origin to its evolution over time, Thyroid peroxidase has left its mark on society, culture and history, generating debates, reflections and analyzes that allow us to better understand its importance. In this article, we will delve into the world of Thyroid peroxidase to discover its many facets and learn more about its meaning in our current context.
Thyroid peroxidase, also called thyroperoxidase (TPO), thyroid specific peroxidase or iodide peroxidase, is an enzyme expressed mainly in the thyroid where it is secreted into colloid. Thyroid peroxidase oxidizes iodide ions to form iodine atoms for addition onto tyrosine residues on thyroglobulin for the production of thyroxine (T4) or triiodothyronine (T3), the thyroid hormones. In humans, thyroperoxidase is encoded by the TPOgene.
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
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 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. 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 thioamide drugs, such as propylthiouracil and methimazole. In laboratory rats with insufficient iodine intake, genistein has demonstrated inhibition of TPO.
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