OxyFile #425

Predominant role of catalase in the disposal of hydrogen peroxide 
within human erythrocytes.

Gaetani GF; Ferraris AM; Rolfo M; Mangerini R; Arena S; Kirkman HN

Division of Hematological Oncology, Istituto Nazionale per la 
Ricerca sul Cancro, University of Genoa, Italy.

Blood, 87: 4, 1996 Feb 15, 1595-9


Purified enzymes were mixed to form a cell-free system that 
simulated the conditions for removal of hydrogen peroxide within 
human erythrocytes. Human glutathione peroxidase disposed of 
hydrogen peroxide (H2O2) at a rate that was only 17% of the rate 
at which human catalase simultaneously removed hydrogen peroxide. 
The relative rates observed were in agreement with the relative 
rates predicted from the kinetic constants of the two enzymes. 
These results confirm two earlier studies on intact erythrocytes, 
which refuted the notion that glutathione peroxidase is the 
primary enzyme for removal of hydrogen peroxide within 
erythrocytes. The present findings differ from the results with 
intact cells, however, in showing that glutathione peroxidase 
accounts for even less than 50% of the removal of hydrogen 
peroxide. A means is proposed for calculating the relative 
contribution of glutathione peroxidase and catalase in other cells 
and species. The present results raise the possibility that the 
major function of glutathione peroxidase may be the disposal of 
organic peroxides rather than the removal of hydrogen peroxide.