title: Reaction of tyrosine oxidation products with proteins of the lens.
abstract: Oxidation of tyrosine in the presence of bovine lens proteins leads to the formation of brown or black melanoproteins. Both tyrosinase and the oxidizing system of ferrous sulphate-ascorbic acid-EDTA are effective. The fluorescence of the lens proteins is both altered and enhanced by the tyrosine-oxidizing systems. Their fluorescence spectra resemble those of urea-insoluble proteins of human cataractous lens and of 1,2-naphthaquinone-proteins of naphthalene cataract. The lens proteins lose their thiol groups and, in acid hydrolysates of treated beta-and gamma-crystallins, a substance has been detected chromatographically that behaves similarly to a compound formed when 3,4-dihydroxyphenylalanine (dopa) is oxidized by tyrosinase in the presence of cysteine. Analysis and behaviour of this substance from hydrolysates of lens proteins suggest that it is a compound of cysteine and dopa.
mesh_terms: D000818:Animals; D001205:Ascorbic Acid; D002386:Cataract; D004156:Catechol Oxidase / Q000378:metabolism; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D002854:Chromatography, Paper; D003459:Crystallins / Q000032:analysis; D003545:Cysteine / Q000032:analysis; D004295:Dihydroxyphenylalanine / Q000032:analysis; D004492:Edetic Acid; D005453:Fluorescence; D007501:Iron; D009285:Naphthoquinones; D010084:Oxidation-Reduction; D011506:Proteins; D013431:Sulfates; D013455:Sulfur; D014443:Tyrosine
chemical_list: D003459:Crystallins; D009285:Naphthoquinones; D011506:Proteins; D013431:Sulfates; D014443:Tyrosine; D004295:Dihydroxyphenylalanine; D013455:Sulfur; D004492:Edetic Acid; D007501:Iron; D004156:Catechol Oxidase; D003545:Cysteine; D001205:Ascorbic Acid