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

Qianyun Han; Fang Liu; Yanling Hao; Yuanying Ni

doi:10.1016/j.ijbiomac.2020.04.225

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

Int J Biol Macromol. 2020 Apr 29:158:977-984. doi: 10.1016/j.ijbiomac.2020.04.225. Online ahead of print.

Authors

Qianyun Han¹, Fang Liu², Yanling Hao³, Yuanying Ni⁴

Affiliations

¹ College of Food Science and Nutritional Engineering, China Agricultural University, No. 17 Qinghua East Road, Beijing 100083, China; National Engineering Research Center for Fruits and Vegetables Processing, Beijing 100083, China; Key Laboratory of Fruit and Vegetables Processing, Ministry of Agriculture, Beijing 100083, China.
² College of Food Science and Engineering, Northwest A & F University, Yang Ling, Shaanxi 712100, China.
³ College of Food Science and Nutritional Engineering, China Agricultural University, No. 17 Qinghua East Road, Beijing 100083, China.
⁴ College of Food Science and Nutritional Engineering, China Agricultural University, No. 17 Qinghua East Road, Beijing 100083, China; National Engineering Research Center for Fruits and Vegetables Processing, Beijing 100083, China; Key Laboratory of Fruit and Vegetables Processing, Ministry of Agriculture, Beijing 100083, China. Electronic address: niyycau@hotmail.com.

PMID: 32360471
DOI: 10.1016/j.ijbiomac.2020.04.225

Abstract

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 °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 °C. The circular dichroism spectrum showed that mPPO contains high α-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.

Keywords: Characterization; Enzyme activity; Membrane-bound polyphenol oxidase; Molecular properties.