作 者：
占坤;杨正利;徐子怡;赖章凤;李军;陈罗君;周四喜;李明玺;甘玉迪
单 位：
修水县茶叶科学研究所;江西农业大学农学院;江西省宁红集团有限公司
摘 要：
为探究适制宁红茶茶树品种多酚氧化酶（Polyphenol oxidase,PPO）的酶学性质，提高宁红茶茶黄素含量，以宁州群体种、宁州2号、大叶龙品种的一芽二叶鲜叶为试验材料，获取膜结合态多酚氧化酶（Membrane-bound polyphenol oxidase,mPPO）和可溶态多酚氧化酶（Soluble polyphenol oxidase,sPPO）粗酶，并进行酶学性质分析。以邻苯二酚为底物，3个茶树品种mPPO比活力均高于sPPO比活力，大叶龙mPPO比活力最高，为（542.59±25.13）U·mg-1，宁州2号的sPPO比活力最低，为（112.57±14.01）U·mg-1。mPPO最适反应温度在40～60℃，sPPO最适反应温度在30～50℃，宁州2号和大叶龙的mPPO最适反应温度最高均为55℃，宁州2号和宁州群体种的sPPO最适反应温度最低为35℃。sPPO最适pH值在7.00～8.50，有1个峰，而mPPO最适pH值在5.00～8.00，有2个峰，宁州群体种的sPPO最适pH值为8.00，宁州2号mPPO最适pH为5.50。mPPO和sPPO对二羟基酚有较强亲和力，其中宁州2号mPPO对邻苯二酚亲和力最强，催化效率最高。抗坏血酸对宁州群体种sPPO抑制效果最好，卤化物抑制剂对适制宁红茶茶树品种sPPO与mPPO活性均无抑制作用，EDTA对适制宁红茶茶树品种mPPO均有活化作用。适制宁红茶茶树品种sPPO和mPPO的热失活遵循一级反应动力学规律，大叶龙mPPO耐热性最好，热敏感性最差，对温度敏感性最弱，而宁州群体种sPPO耐热性最差，热敏感性最强，对温度敏感性最强。结果表明，不同茶树品种间sPPO和mPPO酶特性有一定差异，大叶龙品种mPPO比活力最高，耐热性最好，可为高茶黄素宁红茶加工提供合适酶源。
作 者：
ZHAN Kun;YANG Zhengli;XU Ziyi;LAI Zhangfeng;LI Jun;CHEN Luojun;ZHOU Sixi;LI Mingxi;GAN Yudi;College of Agronomy, Jiangxi Agricultural University;Xiushui Tea Science Research;Jiangxi Ninghong Group Limited Company;
关键词：
Ninghong tea;;polyphenol oxidase;;enzymatic properties
摘 要：
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.
