Purification and characterization of polygalacturonase from the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae)

Abstract

Polygalacturonase from the rice weevil, Sitophilus oryzae (L.), was purified to apparent homogeneity from whole-body extracts of adult insects. This is the first purification reported for a pectinase of animal origin, although our data do not distinguish between an insect or endosymbiotic bacterial genetic origin for the enzyme. Chromatography on cross-linked pectate, Q-Sepharose and, S-Sepharose was employed sequentially in the purification. The properties of the rice weevil enzyme are similar to those of polygalacturonases from bacteria, fungi and plants. The molecular mass of the rice weevil enzyme was estimated to be 38 kDa by SDS-polyacrylamide gel electrophoresis. The K m of the polygalacturonase for pectic acid was 1.1 mg/ml and the pH optimum was about 5.5. The enzyme has an endo mode of action on pectic acid, as determined by comparison of rates of reduction of viscosity and release of reducing groups.