Characterization of membrane-bound polyphenol oxidase from Granny Smith apple (Malus x domestica Borkh.)

摘要

Membrane-bound polyphenol oxidase (mPPO) from the Granny Smith apple was purified and characterized. The enzyme was purified by a factor of 20.53 with a recovery of 1.8%. The molecular weight of purified mPPO was determined to be 65 kDa by electrophoresis and nano-electrospray ionization mass spectrometry. mPPO exhibited its highest activity at a temperature of 35 degrees C and a pH of 7.0 and can be regarded as a diphenol oxidase. A low concentration of SDS (<= 0.5 mM) enhanced the enzymatic activity, whereas mPPO was activated at high concentration EDTA (>= 2 mM). The thermal transition temperature of mPPO was 76.98 degrees C. The circular dichroism spectrum showed that mPPO contains high alpha-helix content, the fluorescence spectroscopy indicated that the tryptophan residues of mPPO are partially buried. The particle size of mPPO was 5-10 nm with a complete structure. The structural characterization of mPPO provided better insights into the regions responsible for its activity. (c) 2020 Elsevier B.V. All rights reserved.