PREDOMINANT ROLE OF CATALASE IN THE DISPOSAL OF HYDROGEN-PEROXIDE WITHIN HUMAN ERYTHROCYTES

Purified enzymes were mixed to form a cell-free system that simulated the conditions for removal of hydrogen peroxide within human erythrocy tes. Human glutathione peroxidase disposed of hydrogen peroxide (H2O2) at a rate that was only 17% of the rate at which human catalase simul taneously removed hydrogen peroxide. The relative rates observed were in agreement with the relative rates predicted from the kinetic consta nts of the two enzymes. These results confirm two earlier studies on i ntact erythrocytes, which refuted the notion that glutathione peroxida se is the primary enzyme for removal of hydrogen peroxide within eryth rocytes. The present findings differ from the results with intact cell s, however, in showing that glutathione peroxidase accounts for even l ess than 50% of the removal of hydrogen peroxide. A means is proposed for calculating the relative contribution of glutathione peroxidase an d catalase in other cells and species. The present results raise the p ossibility that the major function of glutathione peroxidase may be th e disposal of organic peroxides rather than the removal of hydrogen pe roxide. (C) 1996 by The American Society of Hematology.