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Journal of Tea Science ›› 2023, Vol. 43 ›› Issue (3): 356-366.doi: 10.13305/j.cnki.jts.2023.03.003

• Research Paper • Previous Articles     Next Articles

Comparison of Soluble and Membrane-bound Polyphenol Oxidase from Cultivars Suitable to Ninghong Tea Production

ZHAN Kun1, YANG Zhengli1, XU Ziyi1, LAI Zhangfeng1, LI Jun2, CHEN Luojun2, ZHOU Sixi3, LI Mingxi1, GAN Yudi1,*   

  1. 1. College of Agronomy, Jiangxi Agricultural University, Nanchang 330045, China;
    2. Xiushui Tea Science Research, Jiujiang 332400, China;
    3. Jiangxi Ninghong Group Limited Company, Jiujiang 332400, China
  • Received:2023-02-12 Revised:2023-04-20 Online:2023-06-15 Published:2023-06-29

Abstract: In order to investigate the enzymatic properties of polyphenol oxidase (PPO) in cultivars suitable for Ninghong tea production, as well as to increase the theaflavin content in Ninghong tea, one bud and two fresh leaves from ‘Ningzhou population’, ‘Ningzhou 2’ and ‘Dayelong’ were used as raw materials to obtain membrane-bound polyphenol oxidase (mPPO) and soluble polyphenol oxidase (sPPO) crude enzymes and to analyze the enzymatic properties. Using catechol as the substrate, the mPPO specific activity of each cultivar was higher than sPPO specific activity. mPPO specific activity of ‘Dayelong’ was the highest (542.59±25.13 U·mg-1), and sPPO activity of ‘Ningzhou 2’ was the lowest (112.57±14.01 U·mg-1). The optimum reaction temperature for mPPO was 40-60 ℃, the optimum reaction temperature for sPPO was 30-50 ℃, and the highest optimum reaction temperature for mPPO of ‘Ningzhou 2’ and ‘Dayelong’ was 55 ℃. The lowest sPPO optimum reaction temperature for ‘Ningzhou 2’ and ‘Ningzhou population’ was 35 ℃. The optimum pH of sPPO ranged from 7.00-8.50 with one peak, while the optimum pH of mPPO ranged from 5.00-8.00 with two peaks. The optimum pH of sPPO in ‘Ningzhou population’ was 8.00, and the optimum pH of mPPO in ‘Ningzhou 2’ was 5.50. mPPO and sPPO had strong affinity for dihydroxy phenols, and mPPO in ‘Ningzhou 2’ had the strongest affinity for catechol and the highest catalytic efficiency. Ascorbic acid had the best inhibitory effect on sPPO in ‘Ningzhou population’. While halide inhibitors had no inhibitory effect on both sPPO and mPPO activities in tea cultivars suitable for Ninghong tea production. EDTA had an activating effect on mPPO. The thermal deactivation of sPPO and mPPO in these tea cultivars followed the primary reaction kinetics, with mPPO in ‘Dayelong’ having the best thermal resistance, the worst thermal sensitivity, and the weakest sensitivity to temperature. While sPPO in ‘Ningzhou population’ had the worst thermal resistance. The sPPO of ‘Ningzhou population’ was the worst heat-resistance, the highest heat-sensitivity and temperature-sensitivity. The results show that there were some differences in the sPPO and mPPO enzyme properties among the cultivars. Tea cultivar ‘Dayelong’ had the highest mPPO specific activity and the best heat resistance, which provided a suitable enzyme source for the processing of high theaflavin Ninghong tea. This study also provided a theoretical reference for the actual Ninghong tea production.

Key words: Ninghong tea, polyphenol oxidase, enzymatic properties

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