生菜(Lactuca sativa L.)多酚氧化酶特性研究

Characteristics of Polyphenol Oxidase from Romaine Lettuce(Lactuca sativa L.)

以散叶生菜为原料,研究提取液用量、底物浓度、反应体系pH值和温度、抑制剂对生菜多酚氧化酶(PPO)活性的影响。结果表明:以邻苯二酚为底物,生菜PPO在420nm波长下吸光度最大;磷酸缓冲液(mL)与生菜质量(g)比为1.5∶1时,提取液中PPO活性较强;最适pH值为8.0、最适温度为30℃、最适底物浓度为0.3 mol/L。抑制剂对PPO酶抑制效果依次为抗坏血酸﹥柠檬酸﹥NaCl;此外,生菜叶脉中PPO活性为叶片中PPO活性的5.72倍。

Effects of extract amount, substrate concentration, pH value, temperature and inhibitors on PPO activity from romaine lettuce （Lactuca sativa L.） were evaluated. Results showed that PPO displayed hightest absorbance at 420 nm wavelength with catechol as substrate. The optimum ratio of phosphate buffer solution （mL） to lettuce amount （g） was 1.5∶1;The optimal catechol concentration, pH, and temperature of PPO were 0.3 mol/L, 8.0 and 30℃, respectively. Efficiency of inhibitors on PPO was followed by L-ascorbic acid﹥citric acid﹥NaCl. In addition, PPO activity in vein was 5.72-fold higher than that in leaves.