Carbohydrrases in the Gut and the Salivary Gland, and the Nature of the Amylase in the Gut Homogenate of Lygus disponsi LINNAVUORI (Hemiptera : Miridae)

Abstract

Carbohydrases in the gut and the salivary gland and the nature of the amylase in the gut homogenate of Lygus disponsi were investigated in order to compare the role of the gut with that of the salivary gland in respect to the digestion of carbohydrates. In the gut homogenate, amylase, α-glucosidase and β-h-fructosidase were detected, but in the salivary gland homogenate, only amylase was detected. The rate of reaction of the amylase in the gut homogenate decreased in proportion to the increase of the buffer concentration in the reaction mixture. The reducing sugar produced by the action of the amylase increased in proportion to the substrate concentration, while the concentration was below 0.3%. Its increase stopped at concentrations from 0.3 to 1.8%, from which it increased again constantly but slowly. The optimum temperature for the action of the amylase was found to be about 37°C and the optimum hydrogenion concentration for it was pH 5.0 at 37°C. The amylase in the gut homogenate of both fed and starved insects was strongly activated by Cl- and NO3-, and was strongly inhibited by Cu++ and Hg++. THe gut enzyme hydrolyzed starch to produce maltose and glucose as final products. The amylolytic activity of the salivary gland homogenate was always higher than that of the gut homogenate and on the average the former was about twice as active as the latter. In regards to the digestion of carbohydrate, it was suggested that the role of the gut differed from that of the salivary gland.