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The Relative UV Sensitizer Activity of Purified Advanced Glycation Endproducts
Author(s) -
Ortwerth B. J.,
Prabhakaram Malladi,
Nagaraj R. H.,
Linetsky Mikhail
Publication year - 1997
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1997.tb01909.x
Subject(s) - chemistry , singlet oxygen , superoxide , kynurenic acid , ascorbic acid , riboflavin , kynurenine , tryptophan , oxygen , biochemistry , chromatography , amino acid , photochemistry , organic chemistry , enzyme , food science
— 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 μg/mL) generated5–10 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 μmol/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 generated20–60‐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.