Measurement of Plasma Hemoglobin Peroxidase Activity

We described a spectrophotometric method for measuring hemoglobin peroxidase activity in human plasma using o -dianisidine ( o -DA) as the substrate and myeloperoxidase specific inhibitor 4-aminobensoic acid hydrazide (ruling out the probable contribution of myeloperoxidase to the measured parameter value). The optimal conditions (pH 5.5; 2 mM H 2 O 2 ) have been determined, at which hemoglobin makes the main contribution to plasma oxidation of o -DA. A signifi cant positive correlation between hemoglobin peroxidase activity measured by the spectrophotometric method and hemoglobin level measured by the pyridine hemochromogenic method has been detected ( r = 0.624; p