Enzymatic t-butyl hydroperoxide reduction on human erythrocyte membranes--NADPH and GSH dependent activities.

A NADPH-dependent t-butyl hydroperoxide ( TBH )-reducing activity independent of glutathione was found in addition to glutathione peroxidase activity bound to erythrocyte membranes. In "hypotonic" and "isotonic" membranes the NADPH-dependent TBH -reducing activity amounted to about 0.34 mu kat /l red blood cells (RBC) and the glutathione peroxidase activity to 0.32 mu kat /l RBC. The activities do not appear to be additive. The membrane association of the enzymes is independent of ionic strength. Under hypotonic condition about 0.2% of the total cellular catalase activity were bound to the membrane but none in "isotonic" membranes. The bound catalase appears to exhibit a glutathione dependent peroxidase activity. Membrane-bound haemoglobin exhibited a quasi- TBH -reductase activity which was inhibited by azide and cyanide.