Biomaterial Database

Iodination and oxidation of thyroglobulin catalyzed by thyroid peroxidase. 1984

M Nakamura, and I Yamazaki, and H Nakagawa, and S Ohtaki, and N Ui

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 estimated to be 6.7 X 10(7) and 2.3 X 10(7) M-1 s-1 in native (iodine content = 1.0%) and more iodinated (iodine content = 1.2%) thyroglobulins, respectively. This iodine-transferring reaction was stimulated by iodothyronines, similarly as observed in the reaction with free tyrosine. The iodination of thyroglobulin was inhibited by GSH, the inhibition being competitive with thyroglobulin. Thyroglobulin was oxidized in the presence of a thyroid peroxidase system without giving any appreciable change in absorbance around 300 nm. From stopped flow data, the oxidation was concluded to occur by way of two-electron transfer and the rate constant for the reaction of thyroid peroxidase Compound I with thyroglobulin was estimated to be 1.0 X 10(7) M-1 s-1. The stopped flow kinetic pattern was similar to that observed on the reaction with free tyrosine and monoiodotyrosine. About 6 mol of hydrogen peroxide were consumed per mol of thyroglobulin. Thyroid peroxidase catalyzed thyroglobulin-mediated oxidation of GSH, but lactoperoxidase did not.

UI	MeSH Term	Description	Entries
D007453	Iodide Peroxidase	A hemeprotein that catalyzes the oxidation of the iodide radical to iodine with the subsequent iodination of many organic compounds, particularly proteins. EC 1.11.1.8.	Iodinase,Iodothyronine 5'-Deiodinase,Iodothyronine Deiodinase,Iodotyrosine Deiodase,Thyroid Peroxidase,Thyroxine 5'-Deiodinase,Thyroxine 5'-Monodeiodinase,5'-Deiodinase,Deiodinase,Iodotyrosine Deiodinase,Monodeiodinase,Reverse Triiodothyronine 5'-Deiodinase,T4-5'-Deiodinase,T4-Monodeiodinase,Tetraiodothyronine 5'-Deiodinase,Thyroxine Converting Enzyme,Triiodothyronine Deiodinase,5' Deiodinase,5'-Deiodinase, Iodothyronine,5'-Deiodinase, Reverse Triiodothyronine,5'-Deiodinase, Tetraiodothyronine,5'-Deiodinase, Thyroxine,5'-Monodeiodinase, Thyroxine,Deiodase, Iodotyrosine,Deiodinase, Iodothyronine,Deiodinase, Iodotyrosine,Deiodinase, Triiodothyronine,Enzyme, Thyroxine Converting,Iodothyronine 5' Deiodinase,Peroxidase, Iodide,Peroxidase, Thyroid,Reverse Triiodothyronine 5' Deiodinase,T4 5' Deiodinase,T4 Monodeiodinase,Tetraiodothyronine 5' Deiodinase,Thyroxine 5' Deiodinase,Thyroxine 5' Monodeiodinase,Triiodothyronine 5'-Deiodinase, Reverse
D007455	Iodine	A nonmetallic element of the halogen group that is represented by the atomic symbol I, atomic number 53, and atomic weight of 126.90. It is a nutritionally essential element, especially important in thyroid hormone synthesis. In solution, it has anti-infective properties and is used topically.	Iodine-127,Iodine 127
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D010544	Peroxidases		Ovoperoxidase
D005978	Glutathione	A tripeptide with many roles in cells. It conjugates to drugs to make them more soluble for excretion, is a cofactor for some enzymes, is involved in protein disulfide bond rearrangement and reduces peroxides.	Reduced Glutathione,gamma-L-Glu-L-Cys-Gly,gamma-L-Glutamyl-L-Cysteinylglycine,Glutathione, Reduced,gamma L Glu L Cys Gly,gamma L Glutamyl L Cysteinylglycine
D006861	Hydrogen Peroxide	A strong oxidizing agent used in aqueous solution as a ripening agent, bleach, and topical anti-infective. It is relatively unstable and solutions deteriorate over time unless stabilized by the addition of acetanilide or similar organic materials.	Hydrogen Peroxide (H2O2),Hydroperoxide,Oxydol,Perhydrol,Superoxol,Peroxide, Hydrogen
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013056	Spectrophotometry, Ultraviolet	Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Ultraviolet Spectrophotometry
D013552	Swine	Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).	Phacochoerus,Pigs,Suidae,Warthogs,Wart Hogs,Hog, Wart,Hogs, Wart,Wart Hog