Carbohydrases and carbohydrate digestion in the gut of Locusta migratoria

The digestion of various carbohydrates and synthetic substrates by the gut of Locusta migratoria was analysed quantitatively. Maltose, starch, and sucrose were found to be hydrolysed most rapidly, whereas the splitting of cellobiose, trehalose, lactose, and melecitose took place at much slower rates.The absolute carbohydrase activities in foregut and midgut are nearly equal. However, specific activities are much higher in the foregut. Only low activities were found in extracts from the hindgut and salivary glands. The latter show a pattern of sugar splitting which is different from that found in gut preparations.The distribution of carbohydrase activities between the epithelia and lumina of the foregut, midgut, and hindgut and between soluble and particulate fractions were studied. The midgut epithelium is shown to have a particularly high content of enzymes, although some carbohydrases are rather active also in the epithelium of the hindgut. During hunger periods the relative enzymatic activities of the epithelium are distinctly increased.The isolation and purification of the carbohydrases were attempted and a partial separation of individual enzymes was obtained by gel-filtration. These results indicate the presence of at least seven distinct carbohydrases in the locust gut. The molecular weights of the enzymes were estimated by gel-filtration, and K_M values and pH-optima are reported.