For the oxidation of ABTS, the highest Vmax values were obtained for the preparations of the isoenzymes A2A and A2B. These two isoenzyme preparations were able to oxidize ABTS 4- to 5-fold better than the preparation of the well-studied isoenzyme C1A (Table3), rendering our preparations of HRP A2A and A2B particularly interesting for diagnostic bioassays with increased sensitivity.