Irreversible Inactivation of Lactoperoxidase by Excess Hydrogen Peroxide Involving Cleavage of the Catalytic Heme Moiety
Iodination of tyrosyl residues and the coupling reaction to produce the thyroid hormones are catalyzed by one single enzyme, the thyroid peroxidase. In addition to the two substrates, tyrosine and I−, the presence of H2O2 is required. Though the overall pathway for the two reactions has been known for a long time, the molecular mechanism, and especially the regulatory functions of I− and H2O2, are still a matter of debate. In this report we present evidence that H2O2 and I− are not merely essential substrates but, in addition, they may be involved in the regulation of enzyme activity.
KeywordsAtomic Absorption Spectroscopy Native Enzyme Heme Iron H202 Concentration Thyroid Peroxidase
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