Characterization and quantification of the peroxidase in human monocytes

Abstract

1. 1. The properties of the peroxidase in human moncytes have been compared with those of myeloperoxidase in human granulocytes and with those of isolated human mycloperoxidase. 2. 2. The optical difference spectra of the reduced minus the oxidized states of monocyte and granulocyte homogenates show peaks at 472 and 635 nm that are identical with those observed in the spectrum of reduced isolate myeloperoxidase. 3. 3. Electron paramagnetic resonance spectra of monocytes, granulocytes and isolated myeloperoxidase show a rhombic high-spin haem iron signal with g x = 6.90 and g y = 5.07 . 4. 4. Monocyte and granulocyte lystates show a peroxidative reaction with ortho-dianisidine and require the same optimal substrate concentrations. 5. 5. Monocyte and granulocyte homogenates, as well as isolated myeloperoxidase, catalyse the oxidation of iodide by H 2O 2. This reaction has an acid pH optimum of 4.5–5.5. 6. 6. Ingested zymosan particles are iodinated by monocytes as well as by granulocytes. 7. 7. On the basis of these observations we conclude that human monocytes contain myeloperoxidase. 8. 8. The concentration of myelperoxidase in monocytes is about 1.1 · 10 −17 mol per cell. Granulocytes contain three times this amount of myeloperoxidase per cell.