Purification and characterization of an exo-polygalacturonase from Pycnoporus sanguineus

The present work describes the purification and characterization of a novel extracellular polygalacturonase, PGase I, produced by Pycnoporus sanguineus when grown on citrus fruit pectin. This substrate gave enhanced enzyme production as compared to sucrose and lactose. PGase I is an exocellular enzyme releasing galacturonic acid as its principal hydrolysis product as determined by TLC and orcinol-sulphuric acid staining. Its capacity to hydrolyze digalacturonate identified PGase I as an exo-polygalacturonase. SDS-PAGE showed that PGase I is an N-glycosidated monomer. The enzyme has a molecular mass of 42 kDa, optimum pH 4.8 and stability between pH 3.8 and 8.0. A temperature optimum was observed at 50–60 °C, with some enzyme activity retained up to 80 °C. Its activation energy was 5.352 cal mol⁻¹. PGase I showed a higher affinity towards PGA than citric pectin (Km = 0.55 ± 0.02 and 0.72 ± 0.02 mg ml⁻¹, respectively). Consequently, PGase I is an exo-PGase, EC 3.2.1.82.