title: Potentiation of oxidative damage to proteins by ultraviolet-A and protection by antioxidants.
abstract: We have studied the damage of alcohol dehydrogenase (ADH) and glyceraldehyde 3-phosphate dehydrogenase (GAPD) induced by Fe++/EDTA + H2O2 in combination with UV-A (main output at 365 nm). Enzyme inactivation, formation of hydroxyl radicals (measured in the absence of enzymes), increase in protein carbonyls, oxidation of sulfhydryl (SH) groups, loss of native protein fluorescence, and enhanced protease degradation were used to determine protein damage. Hydroxyl radical production was greatly enhanced by the combination of UV-A with Fe++/EDTA + H2O2. The combined treatment increased protein carbonyls but decreased native protein fluorescence and SH groups. The combined treatment caused turbidity in GAPD but not in ADH, whereas trypsin susceptibility was increased more in ADH than in GAPD. These measurements of protein oxidation correlated well with enzyme activities. Glyceraldehyde 3-phosphate dehydrogenase and dithiothreitol were most protective against such damage, while hydroxyl radical and singlet oxygen scavengers were partially effective. Superoxide dismutase had no effect. Thus, UV-A potentiation of protein damage induced by FE++/EDTA + H2O2 appeared to involve hydroxyl radicals and perhaps singlet oxygen but not superoxide radicals. The damage to proteins induced by combination of UV-A with physiological oxidants, iron ions and H2O2 may be relevant to UV-A-induced skin and tissue damage.
authors.affiliation: Department of Food Science and Technology, University of California, Davis 95616.
authors.forename: M L
authors.initials: ML
authors.lastname: Hu
authors.forename: A L
authors.initials: AL
authors.lastname: Tappel
mesh_terms: D000426:Alcohol Dehydrogenase / Q000378:metabolism / Q000528:radiation effects*; D000975:Antioxidants / Q000494:pharmacology*; D004492:Edetic Acid / Q000494:pharmacology; D005296:Ferrous Compounds / Q000494:pharmacology; D016166:Free Radical Scavengers; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism / Q000528:radiation effects*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D011506:Proteins / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D005296:Ferrous Compounds; D016166:Free Radical Scavengers; D011506:Proteins; C055526:Fe(II)-EDTA; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D000426:Alcohol Dehydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases