期刊
APPLIED BIOCHEMISTRY AND BIOTECHNOLOGY
卷 183, 期 1, 页码 426-443出版社
HUMANA PRESS INC
DOI: 10.1007/s12010-017-2455-y
关键词
Exo-polygalacturonase; Catalytic activity; Purification; Kinetics; Thermal inactivation; Thermodynamic parameters
资金
- Higher Education Commission (HEC), Pakistan under an Indigenous Ph.D. 5000 Fellowship Program
An extracellular exo-polygalacturonase (exo-PG) produced by Penicillium notatum was purified (3.07-folds) by ammonium sulfate fractionation, ion exchange, and gel filtration chromatography. Two distinct isoforms of the enzyme, namely exo-PGI and exo-PGII, were identified during column purification with molecular weights of 85 and 20 kDa, respectively, on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme displayed its optimum activity at pH 6.0 and 50 A degrees C and was found to be stable in the slightly acidic pH (ranging from 4.5 to 6.0). Michaelis-Menten parameters, i.e., K (m (app)) and V (max) for pectin hydrolysis, were calculated to be 16.6 mg/mL and 20 mu mol/mL/min, respectively. The enzyme followed biphasic deactivation kinetics. Phase I of the exo-PGI showed half-lives of 6.83 and 2.39 min at 55 and 80 A degrees C, respectively, whereas phase II of the enzyme exhibited a half-life of 63.57 and 22.72 min at 55 and 80 A degrees C, respectively. The activation energy for denaturation was 51.66 and 44.06 kJ/mol for phase I and phase II of the exo-PGI, respectively. The enzyme activity was considerably enhanced by Mn2+, whereas exposure to a hydrophobic environment (urea and sodium azide solution) drastically suppressed the enzyme activity. Results suggest that exo-PGI might be considered as a potential candidate for various applications, particularly in the food and textile industries.
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