Catalase activity of human polymorphonuclear leukocytes

Abstract

In vitro a high proportion of oxygen free radical produced by polymorphonuclear leukocytes (PMNL) is converted to hydrogen peroxide and a number of studies have utilized H2O2 production as measure of free radical production. However, mammalian cells contain enzymes which produce H2O2 directly. Amongst these are the amine oxidase, catalyzing reaction (1). In addition, catalse is present in most cells and contributes to the elimination of H2O2 via reaction (2).                               

RCH2NH2 + H2O  ====>  RCHO + NH4 + H2O2           (1)

2H2O2  ====>  2H2O + O2                                       (2)

Because several enzymes may contribute to H2O2 production and others to its elimination, the aim of the investigation was to show the measurements of H2O2 production may not accurately represent free radical production or the activity of enzymes which produce H2O2 directly. Catalase activity was assayed, in homogenates of isolated PMNL cells, at pH 7.4 and 37°C with 50 nmol H2O2. Values are mean ± s.e. for 6 blood samples, three from each of two adult male donors. The activity was, 2700 ± 500 µmol/h/109 cells. The high catalase activity of these cells indicated that this enzyme may influence the measured H2O2 level.                                                                                                                                 

Key words: polymorphonuclear leukocytes (PMNL), Hydrogen peroxide (H2O2 ), Catalase.