Nutrition Program, School of Biological and Population Health Sciences, College of Public Health and Human Sciences, Oregon State University, Corvallis, OR, USA.
Department of Food Science and Technology, Oregon State University, Corvallis, OR, USA.
J Nutr. 2022 Feb 8;152(2):429-438. doi: 10.1093/jn/nxab400.
Bovine milk κ-casein-derived caseinomacropeptide (CMP) is produced in large quantities during cheese-making and has various biological activities demonstrated via in vitro and in vivo experiments. Previous studies examined protein degradation and peptide release after casein or whey protein consumption. However, whether purified intact CMP that is partially glycosylated survives intact to its presumed site of bioactivity within the gut remains unknown.
The aim of this study was to determine the extent to which purified intact CMP (including glycosylated forms) is digested into peptide fragments within the jejunum of healthy human adults after consumption.
Jejunal fluids were collected from 3 adult participants (2 men and 1 woman, age: 27 ± 7 y; BMI: 23 ± 1 kg/m2) for 3 h after consuming 37.5 g of purified intact CMP. CMP and CMP-derived peptides were isolated from the collected jejunal fluids by ethanol precipitation and solid-phase extraction and identified by MS-based top-down glycopeptidomics. Relative abundances of CMP and CMP-derived peptides were compared qualitatively between the feed and the jejunal fluids.
Intact CMP was dominant in feeding material, accounting for 90% of the total ion abundance of detected peptides, and in very low abundance (<2%) in the jejunal fluids. CMP-derived fragment peptides ranging from 11 to 20 amino acids in length were predominant (accounting for 68-88% of the total peptide ion abundance) in jejunal fluids during 1-3 h post consumption.
This study demonstrates that intact CMP (including glycosylated forms) is mostly digested in the human jejunum, releasing a wide array of CMP-derived peptide fragments. Some of the CMP-derived peptides with high homology to known bioactive peptides consistently survived across 3 h of digestion. Therefore, future research should examine the biological effects of the partially digested form-the CMP-derived fragments-rather than those of intact CMP.
牛乳κ-酪蛋白衍生的酪蛋白巨肽（CMP）在干酪制作过程中大量产生，并通过体外和体内实验证明具有多种生物学活性。先前的研究检查了酪蛋白或乳清蛋白消耗后蛋白质的降解和肽的释放。然而，部分糖基化的完整 CMP 是否完整地存活到其在肠道内预期的生物活性部位仍然未知。
本研究旨在确定在健康成年人消耗后，完整的 CMP（包括糖基化形式）在空肠中被消化成肽片段的程度。
在消耗 37.5 g 纯化的完整 CMP 后 3 小时内，从 3 名成年参与者（2 名男性和 1 名女性，年龄：27 ± 7 岁；BMI：23 ± 1 kg/m2）收集空肠液。通过乙醇沉淀和固相萃取从收集的空肠液中分离 CMP 和 CMP 衍生肽，并通过基于 MS 的自上而下糖肽组学进行鉴定。在饲料和空肠液之间定性比较 CMP 和 CMP 衍生肽的相对丰度。
完整的 CMP 在进料材料中占主导地位，占检测肽总离子丰度的 90%，在空肠液中含量非常低（<2%）。在消耗后 1-3 小时的空肠液中，长度为 11-20 个氨基酸的 CMP 衍生片段肽占主导地位（占总肽离子丰度的 68-88%）。
本研究表明，完整的 CMP（包括糖基化形式）在人体空肠中大部分被消化，释放出广泛的 CMP 衍生肽片段。一些与已知生物活性肽具有高度同源性的 CMP 衍生肽在 3 小时的消化过程中始终存活。因此，未来的研究应该检查部分消化形式——CMP 衍生片段的生物学效应，而不是完整 CMP 的生物学效应。
