乳酸对多酚氧化酶活性与构象的影响

Effect of lactic acid on activity and conformation of polyphenol oxidase

以蘑菇多酚氧化酶(PPO)作为原料,研究了不同浓度的乳酸对PPO的相对酶活性、巯基含量、内源荧光强度和紫外强度的影响。结果表明:PPO的相对酶活性随着乳酸处理的浓度增大而减小,当乳酸浓度达到40mmol/L时,其相对酶活性下降到原酶的1.20%,PPO活性得到基本抑制;随乳酸浓度的增大,巯基含量逐渐减小,当乳酸浓度为30mmol/L时,巯基含量为原酶的81.59%;PPO相对酶活性由100%变化到0.17%时,其相对巯基含量从100%降低为80.09%,二者呈现较好线性关系(R2=0.9861);从紫外吸收光谱和荧光发射光谱的变化可以看出:经不同浓度乳酸处理过后PPO分子发生部分去折叠化,导致酶活性的降低。

Variations on relative activity,sulfhydryl content,fluorescence and UV intensity of mushroom PPO induced by lactic acid were investigated. The results showed that the relative activity of PPO decreased gradually with the increasing of lactic acid concentration,the relative activity of PPO dropped to 1.20% of its original activity at 40mmol/L. The activity of PPO was inhibited significantly by lactic acid at 40mmol/L. By the detection of sulfhydryl content（SH）,the SH content decreased gradually with increasing lactic acid concentration and was only 81.59% at 30mmol/L. The SH content,decreasing from 100% to 80.09%,following residual relative activities,decreasing from 100% to 0.17% ,showed a liner relationship,when citric acid increased from 0 to 50mmol/L（R2=0.9861 ）. When PPO was induced by different concentrations of lactic acid,the conformation of PPO was gradually unfolded which induced the decreasing of relative activity.