Reactive oxygen species responsible for beta-glucan degradation

Abstract

The presence of iron(II) in beta-glucan in solution causes the formation of hydroxyl radical, which further oxidises the polysaccharide. This degradation can be enhanced by the presence of a reducing agent, such as ascorbic acid. In this study we investigated the effect the iron(II) concentration on the hydroxyl radical-mediated degradation of beta-glucan and identified the intermediate species involved in the formation of hydroxyl radicals. An increase in the iron(II) concentration did not have a significant effect on the degradation in the presence of a reducing agent (ascorbic acid), while in the mere presence of iron(II) it accelerates the degradation. The addition of catalase and superoxide dismutase (SOD) prevented the hydroxyl radical driven-degradation of beta-glucan induced by iron(II) or ascorbic acid/iron(II), demonstrating the involvement of both superoxide and hydrogen peroxide in the hydroxyl radical formation. SOD, which catalyses the dismutation of superoxide into hydrogen peroxide, should have stimulated the formation of radicals, since these radicals are generated from the reaction between hydrogen peroxide and iron(II). In the present study, we hypothesise the mechanism of the inhibition of beta-glucan degradation by superoxide dismutase.