|
pubmed:abstractText |
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.
|
