Partial purification and kinetic properties of polygalacturonase from Solanum macrocarpum L. Fruit

Abstract

Background and Objective: Polygalacturonase [Poly (1,4-a-D-galacturonide) glucanohydrolase, E.C 3.2.1.15] is a subclass of pectinase that hydrolyzes the glycosidic linkages between galacturonic acid residues in polygalacturonans. Solanum macrocarpum ripening prompts pectinase production. The objective of this study was to examine the kinetic properties of polygalacturonase from Solanum macrocarpum L. fruit. Methodology: The enzyme was partially purified by ammonium sulphate precipitation and gel filtration. Protein content, polygalacturonase activity and kinetic parameters were determined. Results: The protein content and polygalacturonaseactivity of the fruit juice extracts were 0.63 ± 0.02 mgmL-1 and 45.96+6.31 U mg-1 protein, respectively. A 1.7 and 108.3 fold increase in enzyme activity was achieved by ammonium sulphate precipitation and gel filtration, respectively. The enzyme had a Vmax of 76.92 unitmg-1 protein and Km of 0.92 mg mL-1. The pH profile of the enzyme showed three activity peaks at 3.0,5.5 and 7.0. The enzyme was most active at pH 3.0 and showed optimal activity at 30°C. Rapid release of product was observed within the first 20 min of enzyme incubation. The Zn2+, Ca2+, Mn2+, Pb2+, Fe2+, Cu2+ and EDTA exhibited inhibitory effect on polygalacturonase activity whereas Mg2+ had stimulatory effect on the enzyme. Conclusion: It was concluded that the fruit of Solanum macrocarpum is a rich source of polygalacturonase. The enzyme is favourably comparable with that of a fungi source and could be further exploited for commercial production of the enzyme.