Abstract:

In order to compare the difference in milk fat globule membrane (MFGM) proteins between breast milk and
bovine milk, MFGM were extracted from milk by organic solvent extraction and lysed in SDS-containing lysis buffer for
analysis by liquid chromatography and mass spectrometry (LC-MS) after the removal of SDS using PierceTM detergent
removal spin column. The results were filtered according to the number of unique peptide ≥ 1. A total of 863 and 454
proteins were identified separately in breast milk and bovine milk, including 175 proteins in common, and 688 and 279
proteins unique for breast milk and bovine milk, respectively. Gene Ontology (GO) analysis of 688 specific MFGM proteins
in human milk showed that they were mainly distributed in cell part, cell organelle, and cell membrane, and involved in
biological pathways such as metabolic processes, biological regulation, response to stimulus, immune system process,
reproduction, and so on. These proteins also participated in many molecular functions, such as catalytic activity, binding, transport
activity and enzyme regulation activity. In addition, these breast milk MFGM proteins were involved in some metabolic pathways,
such as aminoacyl-tRNA biosynthesis, pathogenic Escherichia coli infection, fatty acid metabolism, propanoate metabolism,
steroid biosynthesis, lysine degradation, which were not shown in bovine milk. The MFGM proteins in breast milk and bovine
milk had obvious differences. Although some compositions and functions were overlapped, in terms of abundance and metabolic
pathways, the MFGM proteins in bovine milk could not be replaced by those in breast milk.

Key words: milk fat globule membrane proteins, breast milk, bovine milk, functional annotation, metabolic pathway