A variety of proteases release hundreds of endogenous peptide fragments from intact bovine milk proteins. Mass spectrometry-based peptidomics allows for high throughput sequence assignment of a large number of these peptides. Mastitis is known to result in increased protease activity in the mammary gland. Therefore, we hypothesized that subclinically mastitic milks would contain higher concentrations of released peptides. In this work, milks were sampled from three cows and, for each, one healthy and one subclinically mastitic teat were sampled for milk. Peptides were analyzed by nano-liquid chromatography quadrupole time of flight tandem mass spectrometry and identified with database searching. In total, 682 peptides were identified. The total number of released peptides increased 146% from healthy to subclinically mastitic milks (p < 0.05), and the total abundance of released peptides also increased significantly (p < 0.05). Bioinformatic analysis of enzyme cleavage revealed increases in activity of cathepsin D and elastase (p < 0.05) with subclinical mastitis.

中文翻译：

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健康和亚临床乳腺炎牛乳的肽组学分析

多种蛋白酶从完整的牛乳蛋白中释放出数百个内源性肽片段。基于质谱的肽组学允许对大量这些肽进行高通量序列分配。已知乳腺炎会导致乳腺中蛋白酶活性增加。因此，我们假设亚临床乳腺炎乳将含有更高浓度的释放肽。在这项工作中，对三头奶牛的牛奶进行了采样，并为每头奶牛抽取了一只健康的乳头和一只亚临床乳腺炎的乳头以获取牛奶。通过纳米液相色谱四极杆飞行时间串联质谱分析肽并通过数据库搜索进行鉴定。总共鉴定了 682 个肽段。从健康乳到亚临床乳腺炎乳，释放肽的总数增加了 146% (p < 0.05)，并且释放肽的总丰度也显着增加（p < 0.05）。酶裂解的生物信息学分析显示，亚临床乳腺炎组织蛋白酶 D 和弹性蛋白酶的活性增加 (p < 0.05)。