Characterization and partial purification of proteinases from the highly alkaline midgut of the humivorous larvae of Pachnoda ephippiata (Coleoptera: Scarabaeidae)

Proteinases in the humus-feeding larva of Pachnoda ephippiata were partially purified and characterized. Proteinase activity from the midgut was alkali-stable and its pH optimum for activity was about pH 12. Nine proteolytic bands were visible on zymogram gels containing gelatin; one band of 19 kDa was dominant. P. ephippiata mainly employed serine proteinases for digestive proteolysis. The combination of strong midgut alkalinity and midgut proteinases with pronounced alkali stability, a high proteolytic activity on model humic acids, and a large tolerance to high humic acid concentrations would enable the P. ephippiata to gain nutrients from soil by digesting the proteinaceous component of soil humic substances.