Glutathione peroxidase and glutathione reductase activities towards glutathione-derived antioxidants.

A new class of glutathione derivatives with antioxidant properties has been prepared by transformation of the NH2 group into a pyrrole ring with various substitutions at the 2 and 5 positions. Due to steric hindrance and/or hydrophobicity of the 2-5-disubstituted pyrrole ring, the reduced glutathione derivatives are poor substrates of the glutathione peroxidase and do not effectively compete with GSH. The oxidized glutathione derivatives are, in turn, relatively good substrates (Km = 1.5 mM) of the glutathione reductase as compared to natural oxidized glutathione (Km = 0.51 mM) but are not effective competitors of the enzyme. It can be considered that the new glutathione derivatives do not strongly interfere with the natural enzymatic defence against fatty acid hydroperoxides formed during an oxidative stress.