Carbohydrases of the alimentary tract of the desert locust, Schistocerca gregaria Forsk.

Abstract

Carbohydrases, which may or may not be secreted, are present in the salivary glands and in the tissues of the foregut, midgut, and digestive caeca and hindgut. They are found along the whole length of the gut lumen, but the greatest concentration, at least as far as sucrose and starch-digesting enzymes are concerned, is in the crop region of the foregut. Here most of the digestion takes place whereas most of the absorption is from the midgut and caeca. The pH of the alimentary tract increases from pH 5·5 in the foregut to pH 6·2 in the anterior midgut and then to pH 7·0 in the posterior midgut and hindgut. The hydrolysis of a wide range of oligosaccharides can be accounted for by assuming the presence of the following enzymes: α-glucosidase, β-glucosidase, α-galactosidase, and β-galactosidase. β-Fructosidase is absent. Polysaccharides are digested by amylase, β-(1→4)-polyglucosidase, and cellulase. The amount of cellulose digestion is usually very small, but when food is in short supply cellulose might be of nutritional value. The α-glucosidase present in freeze-dried preparations of the gut contents has a pH optimum at 5·4, Km = 0·0137 (molar methyl α-glucoside), Q10 = 2·25, and an activation energy of 14,100 cal/mole; it is relatively thermostable. © 1964.