Ozone-induced formation of O, O′-dityrosine cross-links in proteins

Abstract

Treatment of spectrin, insulin, glucagon and ribonuclease with ozone results in covalent cross-linking of these proteins. This cross-linking is not reversed by treatment with dithiothreitol and thus can not be ascribed to -S-S- bond formation. A concomitant O, O′-dityrosine formation is observed by spectrofluorometric analysis of the protein and by amino acid analysis and thin-layer chromatography of hydrolyzed protein samples. It is highly probable that the observed protein cross-linking should be attributed to interpeptide O, O′-dityrosine bonds. Several authors bave shown before that oxidation of proteins with horseradish peroxidase and H 2O 2 also leads to O, O′-dityrosine formation. Peroxidase-induced O, O′-dityrosine formation in galactose oxidase ( d- galactose:oxygen 6-oxidoreductase, EC 1.1.3.9) causes a strong increase of enzyme activity. In accordance with these observations ozone treatment of galactose oxidase also leads to O, O′-dityrosine formation with a concomitant 8-fold increase of enzyme activity.