Lei Dongfeng,Jiang Dazong,Wang Yili
(School of Life Science and Technology,Xi'an Jiaotong University,Xi'an 710049,China)
Abstract: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 ¡æ,40 ¡æ,45 ¡æ,50 ¡æ, 55 ¡æ, 60 ¡æ,65 ¡æ,70 ¡æ and 75 ¡æ was investigated ,with observation of remarkable decrease within 5 minutes and more slowly decrease rate afterwards, and the optimal temperature is near 35 ¡æ. 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.CuCl2 can activate activity of PPO, and its regression equation with concentration of Cuª¬2+ was also deduced.
Keywords:tobacco leaves;polyphenol oxidase;activity change;activity
inhibition