The influence of γ-irradiation on some biological activities and electrophoresis patterns of wheat grain albumin fraction

Abstract

Water-soluble proteins were extracted from irradiated wheat grain for the purpose of assaying biological activities, reducing sugars content and SDS–PAGE electrophoresis. The differences between samples after γ-irradiation were tested by analysis of variance at the level of significance ( P ⩽ 0.05). Ionising radiation (0.05–10 kGy) caused an increase in the activity of endogenous amylases, statistically significant at doses of 5 and 10 kGy ( P ⩽ 0.05), which was well correlated with the highest extractable protein content. γ-Irradiation of wheat grain at a dose of 0.05 kGy caused an increase of inhibition activity against Sitophilus granarius L. α-Amylase, whereas there was a decrease at 10 kGy ( P ⩽ 0.05). On the other hand, grain irradiated by 0.5 and 1 kGy doses showed a significant increase in inhibition activity against α-amylase of Tribolium confusum Duv. ( P ⩽ 0.05) while at the remaining doses the inhibition activity was on the same level as the control grain. Decrease of Ephesitia kuehniella Zell. α-amylase was observed only at 5 kGy radiation dose ( P ⩽ 0.05). At the remaining doses this activity was comparable to non-irradiated grain. The highest increase of antiamylolytic activity against human saliva α-amylase was noted in albumin proteins of wheat grain treated by γ-radiation doses >0.5 kGy while there were decreases at radiation doses <0.5 kGy ( P ⩽ 0.05). The increase of inhibition activity against hog pancreas α-amylase was noted at radiation doses 0.1 kGy ( P ⩽ 0.05). γ-Radiation doses of 0.05, 0.5 and 1 kGy caused an increase of the antitryptic activity while 10 kGy decreased this activity ( P ⩽ 0.05). SDS–PAGE electrophoresis patterns of albumin sample at 0.1 kGy showed 15 proteins while in the control sample only 11 bands were found. Among studied wheat albumins, the lower protein bands 5 and 8 were detected in wheat grain samples irradiated by 10 and 0.5 kGy, respectively. The differences in inhibitor activities and electrophoretic protein bands of wheat albumin from γ-irradiated wheat grain give additional evidence that these proteinaceous inhibitors against enzymes studied are different in nature.