X-Ray- and Heat-Induced Generation of Hydrogen Peroxide and Hydroxyl Radicals in Aqueous Solutions of L-Amino Acids

摘要

We have studied the effects of 1 mM solutions of L-amino acids on the X-ray- and heat-inducedgeneration of hydrogen peroxide and hydroxyl radicals in phosphate buffer (5 mM, pH 7.4). Hydrogen per-oxide was estimated by enhanced chemiluminescence in the luminol/p-iodophenoltperoxidase system;hydroxyl radicals were detected with a fluorescent probe coumarin-3-carboxylic acid. We demonstrate thatamino acids can be grouped into three categories by their effect on X-ray-induced H20, production: thosethat reduce, increase, and have no influence on H2O, yield. Similar amino acid effects were observed uponheating; however, the composition of respective amino acid groups was different. All amino acids loweredthe X-ray-induced hydroxyl radical production, and the most effective were Cys > His > Phe = Met = Trp Tyr (in descending order). Hydroxyl radical generation induced by heating was inhibited by Met, His, andPhe; enhanced by Ser; and not affected by Tyr and Pro. Thus, amino acids have different effects on the pro-duction of reactive oxygen species by X-rays and heating, and some amino acids appear to be effective nat-ural antioxidants.