Interaction of partially-purified amylases from larval Anagasta kuehniella (Lepidoptera: Pyralidae) with amylase inhibitors from wheat

Abstract

1. 1. Amylase from larvae of the Mediterranean flour moth (MFM), Anagasta kuehniella (Zeller), was partially purified by ammonium sulfate precipitation, glycogen complex formation, and chromatography on Sephadex G-100. 2. 2. The amylase fraction was composed of two pairs of isozymes that were detected by polyacrylamide gel electrophoresis (PAGE). Each pair consisted of a major and a minor monomeric protein with molecular weights estimated with a non-dissociating PAGE technique to be about 51 kDa for the slower migrating pair and 56.5 kDa for the faster migrating pair. 3. 3. Mediterranean flour-moth amylase had an alkaline pH optimum between pH 9.0–9.5, a K m, for soluble starch of 0.037%, and was unstable in acid (pH 4.5–5.0) conditions. Chloride ion did not activate the amylase nor cause a shift in K m or pH optimum. 4. 4. An aqueous extract of wheat acted as a non-competitive inhibitor ( K i = 0.79 μg/200 μ) of MFM amylase. Inhibition occurred through the range pH 5.5 to 9.5. 5. 5. Mediterranean flour-moth amylase was not as sensitive as amylase from two granivorous coleopterans to two purified amylase inhibitors ( ca 10 kDa) from wheat but was inhibited to a greater extent by partially purified wheat fractions that contained higher molecular weight albumins.