Change in carbohydrates of chicken and quail ovomucoids by gamma radiation

Abstract

The radiation effects on the carbohydrates in chicken ovomucoid, a protease inhibitor as a typical allergenic glycoprotein of egg white, were investigated to clarify its role for the trypsin inhibitory activity on irradiation. The trypsin inhibitory activity of chicken ovomucoid decreased exponentially as a function of the radiation dose. In O2, the inactivation of chicken ovomucoid was protected remarkably in comparison to that in N2. With protein blotting, protein was degraded in O2 and aggregated in N2. The patterns of carbohydrate blotting were similar to those of protein blotting. These results show that there could be a structural interrelationship between the active site and carbohydrate moiety. Sugar chains in a low molecular weight fraction (MW<5000) seemed to be released by γ-radiation and those in O2 were higher than in N2. From the high-performance liquid chromatography (HPLC) patterns of the degradation of sugar chains, all peaks of the oligosaccharides decreased with an increase of radiation dose and more remarkable in O2 than in N2. It shows that the oligosaccharides of ovomucoids could be released sighificantly in O2 by the degradation associated with γ-radiation. These results suggest that oxygen could play a protective role in the inactivation of ovomucoids by the removal of reducing species generated by γ-radiation and ionizing radiation could cause overall conformational changes by the degradation and release of oligosaccharides, as well as alter the bioactivity of ovomucoid.