Amino acids (AAs) in milk constitute proteins, not only that, they also play a significant part in the body. However, in-depth analysis of AAs in human milk between different lactation periods and different domains is relatively scarce. Herein, free AAs in human colostrum (FHC) and mature milk (FHM), and insoluble-proteome AAs in human colostrum (IPHC) and mature milk (IPHM) were characterized, using metabolomics method based on iTRAQ combined with HPLC–MS/MS. A total of 35, 35, 30, and 30 AAs were characterized in FHC, FHM, IPHC, and IPHM, respectively. Moreover, 20 and 13 significantly differential amino acids (SDAAs) were identified in FHC vs. FHM group and IPHC vs. IPHM group, respectively. The interaction network of these SDAAs was further analyzed, and the SDAAs of these two groups were found to participate in 31 and 24 differential metabolic pathways, respectively. The profiles of free and insoluble-proteome AAs between human colostrum and mature milk were quite different, and the combination of these AAs could offer a better understanding of the changes in biochemical process in human milk, and could also furnish directions for the research into development of babies nutrition and milk powder.

中文翻译：

---

基于代谢组学研究不同区域之间人初乳和成熟牛奶中全光谱氨基酸变化的新见解

牛奶中的氨基酸（AAs）不仅构成蛋白质，而且还在人体中起重要作用。然而，相对缺乏在不同泌乳期和不同区域之间对人乳中氨基酸的深入分析。在此，使用基于iTRAQ的代谢组学方法结合HPLC-MS / MS，对人初乳（FHC）和成熟牛奶（FHM）中的游离氨基酸AA，人初乳（IPHC）和成熟牛奶（IPHM）中的不溶蛋白质组氨基酸进行了表征。 。FHC，FHM，IPHC和IPHM分别表征了35、35、30和30个AA。此外，在FHC对FHM组和IPHC对IPHM组中分别鉴定出20个和13个显着差异氨基酸（SDAA）。这些SDAA的互动网络进行了进一步分析，发现这两组的SDAAs分别参与31和24条差异代谢途径。初乳与成熟牛奶之间的游离和不溶性蛋白质组氨基酸AA的谱图有很大不同，这些AA的组合可以更好地了解人乳中生化过程的变化，也可以为研究发展提供方向婴儿的营养和奶粉。