Thyroid hormone synthesis and thyroglobulin iodination related to the peroxidase localization of oxidizing equivalents: Studies with cytochrome c peroxidase and horseradish peroxidase

Abstract

Cytochrome c peroxidase (CcP) and horseradish peroxidase (HRP), when combined with a stoichiometric amount of H2O2, form stable compounds I which are known as FeIV R{ring operator} and FeIV \ ̊gp+ structures, respectively. These compounds were assayed in the catalysis of thyroid hormone synthesis and the iodination reaction. As previously shown for the lactoperoxidase FeIV R{ring operator} compound, the CcP FeIV R{ring operator} compound was involved in the coupling and not in the iodination reactions. In contrast, the HRP FeIV \ ̊gp+ compound catalyzed both iodination and hormone formation. The possible role of the different peroxidase-H2O2 compounds in the two sequential reactions, thyroglobulin iodination and thyroid hormone formation, is discussed. © 1985.