title: Iodide-dependent catalatic activity of thyroid peroxidase and lactoperoxidase.
abstract: Thyroid peroxidase (TPO) and lactoperoxidase (LPO) display significant catalatic activity at pH 7.0 in the presence of low concentrations of iodide, based both on measurements of H2O2 disappearance and O2 evolution. In the absence of iodide only minor catalatic activity was detected. The stimulatory effect of iodide could not be explained by protection of the enzymes against inactivation by H2O2. A mechanism is suggested involving an enzyme-hypoiodite complex as an intermediate.
mesh_terms: D002384:Catalysis; D006861:Hydrogen Peroxide / Q000378:metabolism; D007454:Iodides / Q000494:pharmacology*; D007784:Lactoperoxidase / Q000302:isolation & purification / Q000502:physiology*; D010544:Peroxidases / Q000302:isolation & purification / Q000502:physiology*; D013961:Thyroid Gland / Q000201:enzymology*; D014443:Tyrosine / Q000494:pharmacology
chemical_list: D007454:Iodides; D014443:Tyrosine; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase; D010544:Peroxidases