Glutathione as a scavenger of free hemin

The interaction of glutathione and hemin was studied at physiological ionic strength and pH conditions. Formation of a glutathione-hemin complex was assessed from the appearance of spectral changes in the visible region. In the presence of excess cyanide and histidine and upon oxidation of the sulfhydryl group, no complex was formed. From these results it was concluded that the thiol group of glutathione serves as a ligand for the heme iron. A binding constant of 3.1(±0.1) × 104M−1 was calculated by use of a Hill plot. The hemolytic effect of hemin on red cell was much reduced in the presence of glutathione. Since hemolysis results from association of hemin with membrane components its binding in the presence and absence of glutathione was studied. It was found that the affinity of hemin for the cytoskeletal membrane proteins as well as for the membrane lipid core was decreased in the presence of glutathione. It was concluded that glutathione competes with the membranes for hemin and by doing so can defend the membrane from injury by hemin.