烟草中多酚氧化酶的生理生化特征及其活性控制的研究

Physiological and Biochemical Characteristic of Tobacco Polyphenol Oxidase and Control Way for Its Activity

对烟草叶中的多酚氧化酶(PPO)进行了部分纯化,对比了叶中PPO在苗期和田间的活性差异,研究了其活性变化规律,发现生长旺盛期PPO活性高于其他时期.研究了烟叶在不同水势条件下PPO活性变化规律,发现水势过高、过低,PPO活性均较低,在-872.78kPa水势条件下,PPO活性最高,所以细胞中的含水量是影响PPO活性的因素之一.研究了PPO在35℃、40℃、45℃、50℃、55℃、60℃、65℃、70℃和75℃等烘烤温度条件下的热敏感性,发现:酶的最适反应温度为35℃;温度由35℃升至75℃,活性逐渐下降,在每一温度下保持5min,活性趋于稳定.用回归法得出了烟叶中PPO的下降百分数与温度之间的关系式.用双倒数作图法比较了NaDiCa、EDTA、巯基乙醇和硫脲4种常用抑制剂对烟叶中PPO活性的抑制强度,结果表明:同一浓度下它们对PPO的抑制强度依次递减,而NaDiCa抑制效率明显高于其他3种抑制剂;CuCl2可以促进PPO活性,用回归法得出了活力增加百分数与二价铜离子浓度的关系式.

Polyphenol oxidase (PPO) in tobacco leaves was fractionally purified. The activity difference of PPO of tobacco leaves existed in seedling and field stage was analyzed and the water potential condition of the leaves cell and temperature were assayed. It was found that the highest activity of PPO was at water potential of -872.78 kPa and at the stage of the rapid growing and developing period. The water content of the leaves cell is one of the factors which affect PPO activity. The thermal stability of PPO at 35 ℃ ,(40 ℃) ,45 ℃ ,50 ℃ , 55 ℃, 60 ℃ ,65 ℃ ,70 ℃ and 75 ℃ was investigated ,with observation of remarkable decrease within 5 minutes and more slowly decrease rate afterwards , and the optimal temperature is near 35 ℃. Regression equation between inhibition percentage and temperature was established. NaDiCa is the strongest competitive inhibitor followed by ethylene diamine tetraacetie acid, mercapto ethanol and thiourea , and these four inhibitors can inhibit activity of PPO at lower concentration.CuCl_2 can activate activity of PPO, and its regression equation with concentration of Cu^(2+) was also deduced.