Detecting Enzyme Activity: A Case Study of Polygalacturonase

Chemical and physical approaches to monitoring enzyme activity are illustrated using polygalacturonase as the focus enzyme. Polygalacturonase is a depolymerase that catalyzes the hydrolysis of 1,4-glycosidic linkages in linear homogalacturonan regions of pectic polymers. Activity measurements of this enzyme may be based on the generation of new product, such as the generation of reducing sugars, or changes in the rheological properties of the polymer that result as a consequence of catalysis. Two basic assay protocols, reducing sugar- and viscosity-based assays, are presented here. Discussions of approaches to enzyme extraction and critical parameters for maintaining assay specificity are included.