Myeloperoxidase‐Mediated Iodination in Granulocytes

Abstract

The kinetics of the granulocyte iodination of phagocytized yeast cells was studied. The data obtained fitted an enzymatic reaction and the inhibition with specific antiserum indicated that the granulocyte iodination was mediated by the action of myeloperoxidase. Purified myeloperoxidase from the cytoplasmic granules of leukaemic myeloid cells was obtained by gel chromatography and ion exchange chromatography of the granule extract. Electrophoresis after treatment of the protein with dodecyl sulfate indicated a subunit structure. The myeloperoxidase formed spectrally characteristic complexes with hydrogen peroxide and also with iodide and it was shown to catalyze the iodination of yeast cells when a continous supply of hydrogen peroxide was formed by the addition of glucose oxidase. Since the myeloperoxidase mediated iodination of microorganisms in granulocytes is dependent on prior uptake of the microorganism, formation of the phagocytic vacuole, degranulation, hydrogen peroxide formation and finally oxidation of the iodide by the myeloperoxidase‐H 2 O 2 complex it should be useful for detection of defects in the phagocytosis process.