Characterization of the Peroxidase in Human Eosinophils

Abstract

1. Human eosinophils contain a peroxidase that appears to be of the same type as horseradish peroxidase, lactoperoxidase and intestine peroxidase. 2. Electron paramagnetic resonance spectra of human eosinophils show high‐spin ferric heme signals with rhombic symmetry (gx= 6.56, gy= 5.31 and gx= 6.33, gy= 5.59) for the heme group. Part of the more rhombic signal is due to catalase, whereas the other part is completely due to the peroxidase. In addition to these high‐spin heme compounds a low‐spin heme compound is detectable with g values (gx= 3.09, gy= 2.22 and gz= 1.48) characteristic of a bisimidazole heme iron complex. 3. The amount of heme iron derived from the eosinophil peroxidase, determined from electron paramagnetic spectra, is 13.2 × 10−17 mol/eosinophil. This is in good agreement with the pyridine hemochrome spectra which yield a value of 13.5 × 10−17 mol heme iron/eosinophil.

Human eosinophil peroxidase: a novel isolation procedure, spectral properties and chlorinating activity

“…Also, the reduced-oxidized difference spectrum of eosinophil peroxidase is nearly identical to that observed in homogenates of pure patient eosinophils [7]. Thus, in this respect eosinophils from patients with eosinophilia do not differ from those normally present in the circulation.…”

“…Results fig.1, trace B) that a substantial shoulder is present in the spectrum at 450 nm. As shown in [7], this shoulder is due to the eosinophil peroxidase. To calculate the amount of eosinophil peroxidase present in this extract, the absorption coefficient of eosinophil peroxidase is needed.…”

“…From 100 1 human blood 200 mg pure myeloperoxidase can be obtained [8]; it should therefore be pos-sible also to isolate the eosinophil peroxidase. Reduced eosinophil peroxidase is distinctly different from myeloperoxidase in its spectral properties [7], having a Soret peak at 448 nm, whereas the Soret peak of reduced myeloperoxidase is at 472 nm. This difference in peak position makes it possible to monitor spectrophotometrically the purification of the peroxidase during the isolation procedure.…”

“…This value is, however, not yet known and therefore the absorption coefficient of lactoperoxidase which has a spectrum similar to eosinophil peroxidase of the detergent extract of leucocytes, purified myeloperoxidase and eosinophil peroxidase: (A) Detergent extract of leucocytes, 2.65 mg protein/ml in 1% cetyltrimethylammonium bromide, 0.1 M Na,SO, and 0.1 M potassium phosphate (pH 7.3); (B) Myeloperoxidase, 3.7 PM in 100 mM potassiumphosphate(pH 7.3); (C) Eosinophil peroxidase, 2.3 PM in 100 mM potassium phosphate (pH 7.3) and 0.5% Tween 80. [7] was used. The absorption coefficient of lactoperoxidase is 110 mM_' .…”

“…As shown in [7] the amount of haem iron derived from the peroxidase in an eosinophil is -4-times higher than the concentration of myeloperoxidase in a neutrophil. Since white blood cells of normal donors contain 3-S% eosinophils, 12-20% of the total peroxidase (on the basis of haem iron) in a homogenate of white cells must be due to eosinophil peroxidase.…”