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Inhibition Of Cysteine And Aspartyl Proteinases In The Alfalfa Weevil Midgut With Biochemical And Plant-Derived Proteinase Inhibitors, Stephen E. Wilhite, Thomas C. Elden, Joze Brzin, Ann C. Smigocki

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Proteolytic activities in alfalfa weevil (Hypera postica) larval midguts have been characterized. Effects of pH, thiol activators, low-molecular weight inhibitors, and proteinase inhibitors (PIs) on general substrate hydrolysis by midgut extracts were determined. Hemoglobinolytic activity was highest in the acidic to mildly acidic pH range, but was maximal at pH 3.5. Addition of thiolactivators dithiothreitol (DTT), 2-mercaptoethanol (2-ME), or l-cysteine had little effect on hemoglobin hydrolysis at pH 3.5, but enhanced azocaseinolytic activity two to three-fold at pH 5.0. The broad cysteine PI E-64 reduced azocaseinolytic activity by 64% or 42% at pH 5 in the presence or …