Changes in protease, esterase, and phosphatases in the alimentary canal of the silkworm during metamorphosis

Abstract During spinning to the early pupal stage, a decrease in enzyme activity in midgut tissue and a corresponding increase in activity in the midgut contents was found. This suggests transport of enzymes from tissues to lumen contents during metamorphosis. The enzyme activity in the gut contents rose steeply in the pharate adult stage. The intracellular distributions of hydrolases were different in larvae and pharate adults except for esterase. A major-peak of midgut protease in larvae coincided with that of alkaline phosphatase.