Proteolytic Systems in Milk: Perspectives on the Evolutionary Function within the Mammary Gland and the Infant.
Proteolytic Systems in Milk: Perspectives on the Evolutionary Function within the Mammary Gland and the Infant.
复制标题
DOI：
10.1007/s10911-015-9334-3
复制
发表时间：
2015-12
影响因子：
2.5
通讯作者：
Gan J
中科院分区：
文献类型：
--
作者：
Dallas DC;Murray NM;Gan J
牛奶含有多种蛋白水解系统的成分（酶原、活性蛋白酶、蛋白酶抑制剂和蛋白酶激活剂），这些成分部分由血液、部分由乳腺上皮细胞和部分由免疫细胞分泌产生。几十年来，研究人员一直在研究牛奶蛋白酶，因为它们会导致牛奶质量和奶酪生产的重大缺陷。大多数以前的研究已经检查了这些蛋白酶，目的是消除或控制它们的作用。然而，我们最近的肽组学研究表明，这些牛奶蛋白酶在健康牛奶中产生特定的肽，并继续在婴儿的胃肠道内发挥作用。这些发现表明，牛奶蛋白酶在帮助婴儿消化或释放功能肽方面具有进化功能。换句话说，母亲不仅为婴儿提供膳食蛋白质，而且还提供消化它们的方法。然而，牛奶中的蛋白水解是由蛋白酶抑制剂和蛋白酶激活剂的平衡控制的，因此只有一小部分牛奶蛋白在乳腺内被消化。这一规定提出了一个问题：如果蛋白水解对婴儿有益，那么通过蛋白酶抑制剂的存在来防止完全蛋白水解会获得什么好处？除了总结什么是已知的牛奶蛋白水解系统，我们探讨这种蛋白水解平衡可能的进化解释。
Milk contains elements of numerous proteolytic systems (zymogens, active proteases, protease inhibitors and protease activators) produced in part from blood, in part by mammary epithelial cells and in part by immune cell secretion. Researchers have examined milk proteases for decades, as they can cause major defects in milk quality and cheese production. Most previous research has examined these proteases with the aim to eliminate or control their actions. However, our recent peptidomics research demonstrates that these milk proteases produce specific peptides in healthy milk and continue to function within the infant’s gastrointestinal tract. These findings suggest that milk proteases have an evolutionary function in aiding the infant’s digestion or releasing functional peptides. In other words, the mother provides the infant with not only dietary proteins but also the means to digest them. However, proteolysis in the milk is controlled by a balance of protease inhibitors and protease activators so that only a small portion of milk proteins are digested within the mammary gland. This regulation presents a question: If proteolysis is beneficial to the infant, what benefits are gained by preventing complete proteolysis through the presence of protease inhibitors? In addition to summarizing what is known about milk proteolytic systems, we explore possible evolutionary explanations for this proteolytic balance.