多酚氧化酶影响青贮过程中蛋白降解的机理研究

红三叶青贮过程中蛋白质降解率显著低于苜蓿及其它豆科牧草，这一现象常归因于多酚氧化酶。本项目在已搜集的红三叶品种基础上，研究其不同生育期多酚氧化酶活性和底物的变化规律；通过将多酚氧化酶与不同底物共培养，分析培养过程中蛋白降解程度、降解产物和酚类底物的消长，确定多酚氧化酶的最适底物；比较青贮过程中多酚氧化酶及其底物对植物蛋白酶和微生物蛋白酶的作用效果，探讨其对不同肽链内切酶和肽链外切酶活性的特异性作用，进一步阐明多酚氧化酶抑制蛋白降解的机理；挖掘富含多酚氧化酶体系的材料，并将其引入苜蓿青贮中，评价其对苜蓿青贮过程中蛋白降解的影响。本项目不仅为红三叶品种和适宜刈割时期的选择提供理论依据，同时可为改善豆科牧草青贮发酵品质、抑制青贮过程中蛋白降解提供新思路。

Red clover polyphenol oxidase (PPO) has the potential to protect protein against protease during ensiling, leading to lower proteolysis compared with alfalfa and other legume forages. This project will investigate: dynamics of PPO activity and substrates during growing stages; the efficacy of various o-diphenolic and monophenolic compounds in PPO-mediated proteolytic inhibition during ensiling; the effect of PPO on proteolysis by plant or microbial protease and the mechanism of PPO on protein degradation reduction; the effect of PPO on proteolytic activities of endo- and exopeptidases; and the effect of industrial and agricultural by-products with higher PPO activity on proteolysis during ensiling. The results of this study will not only provide theoretical foundation for selection of red clover varieties and suitable cutting period, but also provide new ideas for improving fermentation quality and inhibiting proteolysis during ensiling.