title: Use of an iodide-specific electrode to study lactoperoxidase-catalyzed iodination of l-tyrosine.
abstract: An in vitro method employing an iodide-specific electrode for monitoring lactoperoxidase-catalyzed iodination is described. The method utilized lactoperoxidase, potassium iodide, and a glucose--glucose oxidase system for the generation of hydrogen peroxide and l-tyrosine. As iodination of l-tyrosine proceeded, the free iodide concentration in solution decreased and was monitored by an iodide-specific electrode. The iodide electrode was reliable when compared to a 131I-method for measuring free iodide changes in solution. Increasing concentrations of resorcinol, a well-known inhibitor of thyroid peroxidase-catalyzed iodination, in the reaction mixture resulted in graded inhibition of the initial rate of lactoperoxidase-catalyzed l-tyrosine iodination. This in vitro system can be used to assess inhibitory activity of various antithyroid substances.
mesh_terms: D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D007454:Iodides / Q000032:analysis*; D007457:Iodine Radioisotopes; D007784:Lactoperoxidase; D010544:Peroxidases; D012118:Resorcinols; D013997:Time Factors; D014443:Tyrosine
chemical_list: D007454:Iodides; D007457:Iodine Radioisotopes; D012118:Resorcinols; D014443:Tyrosine; D007784:Lactoperoxidase; D010544:Peroxidases