梨多酚氧化酶同工酶组成及其对茶黄素合成的影响

The effect of PPO isoenzyme on the formation of theaflavin during in vitro oxidation

用垂直平板聚丙烯酰胺凝胶的方法,研究了不同品种梨(丰水梨、贡梨、雪梨、水晶梨、香梨)果实多酚氧化酶同工酶的酶带特征.结果表明,不同品种梨多酚氧化酶同工酶具有相似的酶带,但酶带数目、Rf值及相对分子质量均存在种间差异.丰水梨有11条同工酶带,贡梨7条,雪梨5条,水晶梨和香梨分别为6条和4条.PPO同工酶带Rf值集中于0.40～0.70,其相对分子质量集中于4.5×104～9.4×104.同时研究了多酚氧化酶活性和同工酶组成对茶黄素合成的影响.丰水梨果实多酚氧化酶同工酶谱带最多,酶活性最大,合成茶黄素的能力最强.多酚氧化酶合成茶黄素能力大小顺序为:丰水梨,贡梨,雪梨,香梨,水晶梨.

The isoforms of polyphenol oxidase of pear cultivars fruits were studied by means of the polyacrylamide gel vertical slab electrophoresis. Similar bands were observed in pear cultivars, but the number and width of the bands ＆ Rf value and molecular weight were different among cultivars. 11 bands of PPO activity were visible in fengshui pear eatract. 7 bands of PPO activity were visible in gong pear eatract. 5, 6 and 4 bands were present in xue pear, shuijing pear and xiang pear extract, respectively. Rf value of PPO isoenzymes was between 0.40 and 0.70. Molecular weight of PPO isoenzymes ranged from 45 000 to 94 000. An in vitro model fermentation system, containing tea catechins and crude pear polyphenol oxidase from pear fruits has been used to determine the effect of PPO activity and isoenzyme forms on the formation of theaflavin. The bands of fengshui pear were more than that of other cultivars and its PPO activity is the highest among pear cultivars. The ability to synthesis of theaflavins was in the order： PPO of fengshui pear, PPO of gong pear, PPO of xue pear, PPO of xiang pear and PPO of shuijing pear.