Mechanisms of thyroid peroxidase- and lactoperoxidase-catalyzed reactions involving iodide.
نویسندگان
چکیده
منابع مشابه
Mechanism of iodide-dependent catalatic activity of thyroid peroxidase and lactoperoxidase.
Mechanisms that have been proposed for peroxidase-catalyzed iodination require the utilization of 1 mol of H2O2 for organic binding of 1 mol of iodide. When we measured the stoichiometry of this reaction using thyroid peroxidase or lactoperoxidase at pH 7.0, we consistently obtained a ratio less than 1.0. This was shown to be attributable to catalase-like activity of these enzymes, resulting in...
متن کاملCharacterization of one- and two-electron oxidations of glutathione coupled with lactoperoxidase and thyroid peroxidase reactions.
Glutathione (GSH) was oxidized to GSSG in the presence of H2O2, tyrosine, and peroxidase. During the GSH oxidation catalyzed by lactoperoxidase, O2 was consumed and the formation of glutathione free radical was confirmed by ESR of its 5,5'-dimethyl-1-pyrroline-N-oxide adduct. When lactoperoxidase was replaced by thyroid peroxidase in the reaction system, the consumption of O2 and the formation ...
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Propylthiouracil (PTU) and methimazole (MMI) are the most commonly used antithyroid drugs. The available data suggest that these drugs may block the thyroid hormone synthesis by inhibiting the thyroid peroxidase (TPO) or diverting oxidized iodides away from thyroglobulin. It is also known that PTU inhibits the selenocysteine-containing enzyme ID-1 by reacting with the selenenyl iodide intermedi...
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Flavoproteins are a class of enzymes catalyzing a very broad spectrum of redox processes by different chemical mechanisms. This review describes the best studied of these mechanisms and discusses factors possibly governing reactivity and specificity.
متن کاملIodination and oxidation of thyroglobulin catalyzed by thyroid peroxidase.
The kinetics of iodination and oxidation of hog thyroglobulin were studied with purified hog thyroid peroxidase and the results were compared with the reactions of free tyrosine. From Lineweaver-Burk plots and on the basis of a value of 0.83 for delta epsilon mM at 289 nm/iodine atom incorporated, the rate constant for transfer of an assumed enzyme-bound iodinium cation to thyroglobulin was est...
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ژورنال
عنوان ژورنال: Journal of Biological Chemistry
سال: 1984
ISSN: 0021-9258
DOI: 10.1016/s0021-9258(18)89814-3