Partial Purification and Kinetic Properties of Polygalacturonase from Chrysophyllum albidum G. Don Fruit

Abstract

Polygalacturonase is the major pectic enzyme responsible for hydrolysing pectic substances into their monomeric units. This study evaluated the kinetic properties of extracted and partially purified polygalacturonase from Chrysophyllum albidum fruit. Polygalacturonase was extracted from Chrysophyllum albidum fruit and partially purified using ammonium sulphate precipitation (80% saturation), dialysis, and gel filtration (Sephadex-G 100). Protein content and polygalacturonase activity were assayed, and the effects of pH, temperature, and substrate concentration on the enzyme activity were determined. The protein concentration and polygalacturonase activity for the ripe fruit were 1.35 mg/mL and 76.35 U/mg protein, respectively, while for the unripe fruit, it was 0.925 mg/mL and 1.59 U/mg protein. Upon partial purification, five fractions (fraction 18, 21-24) had the highest polygalacturonase activity. The optimum pH and temperature for Chrysophyllum albidum juice extract were 4.5 and 40°C, respectively. The enzyme activity increased with an increase in substrate concentration. The Vmax for polygalacturonase was 4.42 U/mg protein, and Km was 1.38 mg/mL. In conclusion, Chrysophyllum albidum fruit is a source of polygalacturonase which could be explored.