title: The endopeptidase-resistant protein fraction from human cataractous lenses.
abstract: With aging and cataract formation, modifications in absorption and fluorescence of the human lens proteins are observed. These changes have been investigated by the examination of the endopeptidase-resistant fraction isolated from human cataractous lenses. This fraction is highly enriched in atypical fluorescence and absorption (i.e. not attributable to tryptophan, tyrosine or phenylalanine). It has a molecular weight of approximately 3000, is enriched in acidic amino acids and has only a 280 nm shoulder in its u.v. spectrum. The material does not contain detectable levels of malondialdehyde or N-formylkynurenine. Upon acid hydrolysis the fluorescence and u.v. spectra remain unchanged with only a minor degree of cleavage observed. Structural studies on some of the cleavage products indicated the presence of oxindolyl alanine and kynurenine. These compounds could result from photo-oxidation of tryptophan.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002386:Cataract / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003459:Crystallins / Q000378:metabolism*; D010450:Endopeptidases; D006801:Humans; D066298:In Vitro Techniques; D007737:Kynurenine / Q000032:analysis; D000078183:Oxindoles; D013053:Spectrophotometry; D014364:Tryptophan / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D000596:Amino Acids; D003459:Crystallins; D000078183:Oxindoles; C011963:beta-3-oxindolylalanine; D007737:Kynurenine; D014364:Tryptophan; D010450:Endopeptidases