Abstract
Pectin methylesterase (PME) (3.1.1.11) is the pectin degrading enzyme which catalyses the hydrolysis of pectin methylester group, resulting in de-esterification. PME is widely distributed in plants, fungi, yeast and bacteria. In the present study, PME was extracted from tomato by using 8.8% NaCl (4°C). The crude enzyme precipitated with 60% ammonium sulphate resulted in 1.02 fold purification of the enzyme. The purification was done by ion exchange chromatography using DEAE-Cellulose column. This resulted in 1.82 fold purification of the enzyme. The molecular weight of purified enzyme was determined by SDS-PAGE which was found to be 34.0 kDa. During characterization of the purified enzyme, the maximum activity was found at temperature 50°C, pH 6.5, reaction time 45 min. Citrus pectin was the best substrate for maximum enzyme activity. The enzyme did not require any metal ion to express its activity, enzyme was found to be very stable at 4°C and at 50°C the enzyme was stable upto 2 h as it retained 70% of its activity. The Km and Vmax values of the enzyme were found to be 0.115 mg/ml and 1.03 μmol/ml/min. PME enhanced the pectin degradation process in apple juice clarification in combination with polygalacturonase and increased %T650 from 1.7% to 5.6%.
Keywords: Clarification, ion exchange chromatography, pectin metylesterase, purification, SDS-PAGE, thermostability
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