Purification, properties and heat inactivation of pectin methylesterase from apple (cv Golden Delicious)

Pectin methylesterase from apple (cv Golden Delicious) was extracted and pu rified by affinity chromatography on a CNBr-Sepharose(R)-PMEI column. A sin gle pectin methylesterase peak was observed. Isoelectric points were higher than 9. Kinetic parameters of the enzyme were determined as K-m = 0.098 mg ml(-1) and V-max = 3.86 mu mol min(-1) ml(-1) of enzyme. The optimum pH of the enzyme was above 7.5 and its optimum temperature was 63 degrees C. The purified PME required the presence of NaCl for optimum activity, and the s odium chloride optimum concentration increased with decreasing pH (from 0.1 3 M at pH 7 to 0.75 M at pH 4). The heat stability of purified PME was inve stigated without and with glycerol (50%), and thermal resistance parameters (D and Z values) were calculated showing that glycerol improved the heat r esistance of apple PME. (C) 2000 Society of Chemical Industry.