Purification and Characterization of a Novel Protopectin-Solubilizing Enzyme from Aspergillus niger Z-25 |
| |
Authors: | Zhang Yiqing Lu Fengxia Bie Xiaomei |
| |
Affiliation: | College of Food Science and Technology , Nanjing Agricultural University , Nanjing, China |
| |
Abstract: | A mutant, Aspergillus niger Z-25 derived from A. niger XZ-131 with N+ supplementation, produced a protopectin-solubilizing enzyme (protopectinase). The enzyme was purified to homogeneity by a procedure involving ammonium sulfate fractionation and gel chromatographies on DEAE-Sephadex A-50 and Sephadex G-100 columns. The molecular weight of the protopectinase was estimated at 68.4 KD by SDS-polyacrylamide gel electrophoresis. The enzyme was stable from pH 3.0 to 7.0 and up to 60°C. The optimum pH and temperature for enzyme activity was 4.0 and 50°C, respectively. The purified enzyme had 268-U/mL PPase (protopectinase) activity on citrus protopectin, and also showed 100-U/mL PGase (polygalacturonase) activity, which catalyzed the hydrolysis of polygalacturonic acid. The Km value for protopectin was 0.215 mg/mL, while the Km value for polygalacturonic acid was 39.09 mg/ml. The PPase/PGase q-value was 2.68, more than 0.5. Therefore the enzyme was considered a novel pectinase and classified as protopectinase. |
| |
Keywords: | Aspergillus niger protopectinase enzyme purification enzyme characterization |
|
|