US Dairy Forage Research Center, USDA-Agricultural Research Service, Madison, Wisconsin 53706, USA.
J Agric Food Chem. 2010 Jan 27;58(2):959-66. doi: 10.1021/jf903555e.
Producing high quality forage remains a challenge due to potential protein degradation during ensiling. Ten grass species and four cereals were screened for proteolytic inhibition, polyphenol oxidase (PPO) activity, and the presence of soluble PPO substrates. In orchardgrass, ryegrass, smooth bromegrass, and meadow fescue extracts, the addition of caffeic acid resulted in 70-98% reduction in proteolysis for both greenhouse and field grown environments. These same grass extracts exhibited 10- to 1000-fold higher PPO activity compared to all other grasses and cereals, depending on the substrate supplied and environment grown. Chlorogenic acid and caffeic acid were the two abundant soluble o-diphenols. Tall fescue and timothy exhibiting low PPO activity contained the highest levels of chlorogenic acid (3-11 micromol g(-1) FW): 10- to 100-fold more than any o-diphenol in all other grasses. These results suggest that several grass species contain PPO activity, but may lack appropriate o-diphenol substrates to effectively inhibit proteolysis during ensiling while other grasses lack PPO activity but contain potential soluble substrate. Environmental factors appear to influence these parameters, creating an opportunity to exploit and enhance proteolytic inhibition during ensiling by genetic manipulation.
由于青贮过程中潜在的蛋白质降解，生产高质量的饲料仍然是一个挑战。十种草类和四种谷物被筛选出来，以检测其对蛋白质水解的抑制作用、多酚氧化酶（PPO）活性以及可溶性 PPO 底物的存在。在果园草、黑麦草、光滑雀麦和草地羊茅的提取物中，添加咖啡酸可使温室和田间生长环境中的蛋白质水解分别减少 70-98%。这些相同的草类提取物表现出比所有其他草类和谷物高 10-1000 倍的 PPO 活性，具体取决于所提供的底物和生长环境。绿原酸和咖啡酸是两种丰富的可溶性邻二酚。低 PPO 活性的高羊茅和梯牧草含有最高水平的绿原酸（3-11 微摩尔 g(-1)FW）：比所有其他草类中的任何邻二酚都高 10-100 倍。这些结果表明，几种草类含有 PPO 活性，但可能缺乏适当的邻二酚底物，无法在青贮过程中有效抑制蛋白质水解，而其他草类缺乏 PPO 活性，但含有潜在的可溶性底物。环境因素似乎会影响这些参数，为通过遗传操作在青贮过程中利用和增强蛋白质水解抑制提供了机会。
