The Peroxidase-like Activity of the Hemoglobin-Haptoglobin Complex

There is a conflict in the literature as to whether haptoglobin enhances or inhibits the peroxidase like activity of hemoglobin. This con-flict arises from: 1. the effect of the concentration of H2O24) on the activity, 2. the use of different parameters to express the activity. In our own experience using 0-tolidine as the donor, we found that, depending on the concentration of H2O2, activation or inhibition by haptoglobin was observed when the maximum color development was the parameter for the activity. With low concentrations of H2O2 activation and with higher concentrations of H2O2 inhibition was found. However, when the initial reaction rate was used to express the activity, there always was activation regardless of the peroxide concentration. The sequence of events when H2O2 is added to HgbO2 and HgbO2: Hp and Methgb and Methgb: Hp was followed by observing changes in the spectra. The results from the change of the spectra together with the reaction rate of curves of the peroxidase reactions lead us to the conclusion that the complex formed between hemoglobin and haptoglobin enhances the peroxidase like activity of hemoglobin and that it also increases the susceptibility to the destruction by H2O2. Widersprechende Resultate in der Literatur darüber, ob Haptoglobin die peroxydaseähnliche Aktivität von Hämoglobin beschleunigt oder hemmt, lassen sich auf zwei Ursachen zurückführen: 1. den Effekt der Konzentration von H2O2 auf die Enzymaktivität und 2. den Ge-brauch verschiedener Parameter für die Enzymaktivität.