Characterization and partial purification of gut proteinases of Spodoptera exigua Hubner (Lepidoptera: Noctuidae)

Proteolytic activity present in the luminal contents of larval guts of the beet army worm, Spodoptera exigua (Hubner), was characterized, Separation of gut proteins by SDS-PAGE and subsequent incubation with proteinase substrates visualized six separate activities, with apparent molecular masses that ranged from 29 to 110 kDa, Preincubation of the gel with specific low molecular weight inhibitors revealed the specificities of the separated proteinase activities, Five activity bands behaved as serine proteinases, but a sixth band, P31, responsible for 21% of total proteinase activity was susceptible to cysteine proteinase inhibitors, P31, P35, and P45 were subsequently partly purified by anion exchange chromatography and further characterized with specific inhibitors and substrates.