Dietary modulation of α-amylase activity in eight geographical strains of Sitophilus oryzae and Sitophilus zeamais
1988
Baker, J.E.
Rank transformation of specific activity values of α-amylase across four strains of Sitophilus oryzae (L.) and four strains of S. zeamais Motschulsky indicates that levels of these predominant enzymes are highest in adults feeding on hulled barley or long-grain brown rice. Intermediate activity levels are found in weevils feeding on yellow corn (maize) and lowest levels are found in wheat-fed weevils. Although extracts prepared from barley contain inhibitory activity against two purified isoamylases from S. oryzae, levels of the naturally-occurring α-amylase inhibitors against these two enzymes are about 2.2-fold and 6.1-fold, respectively, more concentrated in wheat. Ingestion of these amylase inhibitors and formation of an inactive enzymerinhibitor complex with previously secreted amylase may account for the lower activity of amylase in weevils of both species feeding on wheat. Amylase levels across all strains feeding on a given diet are about 2-fold higher in S. oryzae than in S. zeamais. Significant differences in activity levels were also found between strains in both species. Since α-amylase is a predominant digestive hydrolase in these species, the degree to which cereal diets affect amylase levels may indicate their suitability as potential hosts.
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