Human lens βs- and γA-crystallins exhibitvery similar tryptophan fluorescence emission maxima (329 nm). γA isolated from infant human lenses is photo-oxidized by 300 nm irradiation and forms water-insoluble aggregates; βs or γA from young human lenses form a small amount of water-soluble crosslinked species. At least part of the mechanism of photodamage by 300 nm irradiation is photogeneration of the oxidant H2O2 via the generation of O2- radical, this reaction occurs via photosensitization by the tryptophan photo-oxidation product N-formylkynurenine (N-FK) or related species. These results indicate that even though the tryptophan residues of βs- and γA-crystallins are in hydrophobic (buried) microenvironments as compared to those of the α- and β-crystallins, the photogeneration of N-FK is sufficient to produce O2- and H2O2.
|Number of pages||8|
|Journal||Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular|
|State||Published - Aug 31 1989|
- Human lens
- Hydrogen peroxide