PARTIAL-PURIFICATION AND CHARACTERIZATION OF PEACH PECTINESTERASE

Pectinesterase (EC 3.1.1.11) was extracted from peaches (Prunus persica) and partially purified by preparative free solution isoelectric focusing. On SDS-PAGE gels, protein bands at 36.3 and 33.9 kilodaltons represented the major bands; minor bands were observed at 108.4, 40.7, and 17.0 kilodaltons. The pH optimum for pectinesterase activity in the partially purified extract was 8.0. The enzyme was stable at 30-degrees-C for 30 min between pH values of 5 and 8. Peach pectinesterase is stable when heated at 55-degrees-C for 5 min in 0.1 M NaCl, 50 mM sodium phosphate, pH 7, buffer. However, residual activity decreased to 23% at 65-degrees-C for 5 min and was inactivated at 70-degrees-C for 5 min. The energy of activation of peach pectinesterase was determined to be 34,600 J/mol-degrees-K. The Q10 between 30-degrees-C and 60-degrees-C was estimated to be 1.5-1.6.