The condensing effects of egg lecithin and cholesterol on triolein monolayers are inhibited by substitution of one saturated acyl chain in the triacylglycerol

1. u.v. radiations and copper acetate, as free radical generating systems, determine a significant diminishing of glucose-6-phosphate dehydrogenase activity in the homogenates of Saccharomyces cerevisiae. 2. The inactivation is proportional to the concentration of the formed free radicals, existing a direct dependence on the action time of the free radicals generating systems and on the irradiation dose. The decrease of the enzyme catalytic activity is correlated with the increase of the malondialdehyde concentration. 3. The affinity for the substrate of the enzyme under the action of free radicals does not change significantly compared to the native enzyme: the Km value for NADP is halved, whilst that for glucose-6-phosphate remains unchanged. 4. The electrophoretic study shows evidence of five electrophoretic bands with enzymatic activity in the native extract and the disappearance of one molecular form under the free radical action.