Digestive amylase from the larger grain borer, Prostephanus truncatus Horn

A combination of ion-exchange chromatography, preparative electrophoresis a nd gel filtration chromatography allowed a 1209-fold purification of one of the two major digestive alpha-amylases from larvae of the larger grain bor er, Prostephanus truncatus Horn. The purified enzyme showed a molecular mas s of 60.2 kDa, an isoelectric point of 4.7 and an optimal pH for activity o f 6.0. The enzyme was heat labile and it was recognized by proteinaceous in hibitors from amaranth seeds (Amaranthus hypochondriacus), whereas extracts from maize (Zea mays) and tepary bean (Phaseolus acutifolius) produced ver y low inhibition. When the enzyme was measured at different stages of devel opment, maximal activity was found in the second instar larvae. Activity dr astically decreased to a very low level during the pupae stage and increase d again at the adult stage. A zymogram of the different developmental stage s showed two main bands of a-amylase activity, which almost disappeared at the pupae stage to increase again during the adult stage, revealing a new, smaller band. This new band may be required for a better adaptation of the adult insect to its new environment. (C) 2000 Elsevier Science Inc. All rig hts reserved.