PURIFICATION AND CHARACTERIZATION OF ENDO‐POLYGALACTURONASE FROM Rhizopus arrhizus

An endo‐polygalacturonase (RAPG) from Rhizopus arrhizus grown on rotted apricot has been purified and characterized. Through dialysis, ammonium sulfate fractionation, and successive chromatography on DEAE‐cellulose, Sephadex G‐100 and Sephadex G‐75 columns, a 274‐fold purification was achieved. RAPG was stable at pH 3.8–6.5. Its optimum activity was at pH 5.0. The activation energy (Ea) was 11.9 Kcal/mole. The Q 1 0 value was 2.01 between 20° and 30°C. RAPG has a V max at 1.430 μmoles reducing product/min, and K m at 0.054% pectic acid (DP = 70). Both sodium and potassium ions stimulated RAPG activity in the 0.05–0.10M range. Tannic acid was an effective inhibitor, while chlorogenic, caffeic, p‐coumaric and gallic acids were not. The molecular weight of RAPG was 30,270 by SDS‐gel electro‐phoresis. Both viscosity drop and thin layer chromatography of the end products study proved that RAPG performed a random mechanism in the depolymerization process. RAPG also showed a synergistic effect when tomato pectinesterase was added to the reaction mixture with pectin as the substrate.