title: The relative UV sensitizer activity of purified advanced glycation endproducts.
abstract: The oxidation products of ascorbic acid react with lens proteins to form advanced glycation endproducts (AGE) that are capable of generating reactive oxygen species when irradiated with UVA light. L-Threose, the most active of these oxidation products, was reacted with N-acetyl lysine and six AGE peaks were isolated by RP-HPLC. Each peak exhibited fluorescence and generated superoxide anion and singlet oxygen in response to UV light. Solutions of these AGE peaks (50 micrograms/mL) generated 5-10 nmol/mL of superoxide anion during a 30 min irradiation. This activity was 100-fold less than the superoxide anion generated by kynurenic acid and 400-fold less than riboflavin. Ultraviolet irradiation generated from 1.2 to 2.7 mumol/mL of singlet oxygen with the purified threose AGE compounds. This activity was similar to that seen with other purified AGE compounds (pentosidine, LM-1 and Ac-FTP) and with kynurenine and 3-OH kynurenine. This considerable singlet oxygen formation, however, was still 40-fold less than that obtained with kynurenic acid and 100-fold less than riboflavin under the same irradiation conditions. In spite of this lower sensitizer efficiency, the purified AGE generated 20-60-fold more singlet oxygen on a weight basis than either crude ascorbic acid glycated proteins or a preparation of water-insoluble proteins from aged normal human lenses. On a molar basis, therefore, AGE could account for the sensitizer activity in these protein preparations if they represented less than 1% of the total amino acids.
authors.affiliation: Mason Eye Institute, University of Missouri, Columbia 65212, USA. Beryl_Ortwerth@muccmail.missouri.edu
authors.forename: B J
authors.initials: BJ
authors.lastname: Ortwerth
authors.forename: M
authors.initials: M
authors.lastname: Prabhakaram
authors.forename: R H
authors.initials: RH
authors.lastname: Nagaraj
authors.forename: M
authors.initials: M
authors.lastname: Linetsky
mesh_terms: D017127:Glycation End Products, Advanced / Q000096:biosynthesis*; D006801:Humans; D017319:Photosensitizing Agents / Q000494:pharmacology*; D017382:Reactive Oxygen Species; D014466:Ultraviolet Rays
chemical_list: D017127:Glycation End Products, Advanced; D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species