PREVENTION OF LENS PROTEIN GLYCATION BY TAURINE

Modifications in lens protein structure and function due to nonenzymic glycosylation and oxidation have been suggested to play a significant role in the pathogenesis of sugar and senile cataracts. The glycation reaction involves an initial Schiff base formation between the protei n NH2 groups and the Carbonyl group of a reducing sugar. The Schiff ba se then undergoes several structural modifications, via some oxidative reactions involving oxygen free radicals. Hence certain endogenous ti ssue components that may inhibit the formation of protein-sugar adduct formation may have a sparing effect against the cataractogenic effect s of sugars and reactive oxygen. The eye lens is endowed with signific ant concentration of taurine, a sulfonated amino acid, and its precurs or hypotaurine. It is hypothesized that taurine and hypotaurine may ha ve this purported function of protecting the lens proteins against gly cation and subsequent denaturation, in addition to their other functio ns. The results presented herein suggest that these compounds are inde ed capable of protecting glycation competitively by forming Schiff bas es with sugar carbonyls, and thereby preventing the glycation of lens proteins per se. In addition, they appear to prevent oxidative damage by scavenging hydroxyl radicals. This was apparent: by their preventiv e effect against the formation of the thiobarbituric acid reactive mat erial generated from deoxy-ribose, when the later was exposed to hydro xyl radicals generated by the action of xanthine oxidase on hypoxanthi ne in presence of iron.