Human milk is full of bioactive components that are crucial for infants’ health and development. This thesis focused on the most multifunctional part, proteins in human milk.
We first gave a general introduction into the human milk proteins, endogenous peptides and their post-translational modifications (PTMs) on their regulatory factors, known functionalities, and how to apply mass spectrometry in the analysis of human milk proteins. We then monitored the personalized quantitative changes of individual proteins and endogenous peptides, as well as their PTMs, especially N-glycosylation, during lactation. We demonstrated that the difference between individuals was more substantial than the differences observed over the lactation period within a single individual, emphasizing how personalized profiling is critical. We also illustrated the lactational changes were in line with the developing needs of infants.
Besides human proteins, we showed the existence of non-human proteins mostly cow milk proteins in human milk. For the glycosylated modification, we also devoted to method development in improving the quantification and confidence of the identification of glycopeptides and comprehensively characterizing the intact proteins. With these new methods, we could map and quantify one of the most complete N-glycosylation inventories to date in human milk, and reveal new modifications of a protein named complement component C8.