Effect of sulfur-containing amino acids and peptides on the free-radical fragmentation of biologically active phospho derivatives of glycerol

Abstract

The effects of sulfur-containing amino acids and peptides (cysteine, N-acetylcysteine (NAC), methionine, methionine sulfoxide (MetO), taurine (Tau), glutathione (GSH, GSSH), cysteinylglycine, and glutamylcysteine) on the free-radical degradation of glycero-1-phosphate and dimiristoyl phosphatidylglycerol with phosphoether bond rupture induced by γ-radiation or the Fe²⁺(EDTA)(Cu²⁺)–H₂O₂–(ascorbate) systems have been studied. In the case of a radiation-initiated process, thiols exert the greatest radioprotective effect in a concentration-dependent manner, and the action of MetO and Tau is neutral. In the case of Cu²⁺- mediated fragmentation, all of the test compounds with exception of Tau and NAC inhibit the process. The action of the test compounds on the fragmentation mediated by the Fe²⁺/EDTA–H₂O₂ (Fe²⁺–H₂O₂–ascorbate) systems can be either anti(pro)oxidant or neutral. In this case, all of the thiols other than glutamylcysteine exert an activating effect.