Reviewing the data available in the literature and their own findings, the author consider the role of enzymatic mechanisms in the regulation of lipid peroxidation in the living cells. The paper provides a good evidence that phospholipase A_2 hydrolysis for reduction of hydroperoxy-derivatives of unsaturated phospholipids by non-selenic glutathione S-transferase is not obligatory moreover glutathione S-transferase may be inhibited by the products of phospholipase A_2 hydrolysis -by free unsaturated fatty acids. On the other hand, Se-contained glutathione peroxidase is capable of reducing unsaturated hydroperoxy-acyls of membrane phospholipids only if the phospholipids have been hydrolyzed by phospholipase A_2 and this enzyme is not inhibited in the presence of free fatty acids. It can be suggested from the results that in normal conditions glutathione S-transferase catalyzes direct reduction of oxidized membrane phospholipid acyls, but during pathological stations, when the products of phospholipase-mediated hydrolysis are accumulated (such as tissue ischaemia), the major role in lipoperoxides detoxification in the cells belongs to Se-containing glutathione peroxidase. In addition the accumulation of primary products (hydroperoxy- and hydroxy-derivatives) of polyunsaturated acyl oxidative metabolism in the phospholipid membranes induced the changes in the membrane fluidity, that were opposite to those observed upon cholesterol incorporation into membranes. It was found that antioxidative enzymes such as superoxide dismutase and glutathione peroxidase may play a leading role in the prevention of the pancreas 3-cells in vivo from reactive oxygen species injury in alloxan-treated rats.
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