Besides the polar lipids, the outer layer of MFGM contains a number of glycosylated and non-glycosylated proteins. Proteomic analysis has revealed at least 191 different known proteins in human MFGM, and comparable numbers in bovine milk protein concentrates. While quantitatively these only represent 1% to 2% of total milk protein content, MFGM proteins are of significant interest because many are known to have bioactive and potentially beneficial properties; almost half of identified proteins have membrane/protein trafficking or cell signaling functions. The glycosylated proteins, including mucins (MUC-1, MUC-4, MUC-15), butyrophilin, lactadherin, and CD36, have been suggested to enhance triacylglyceride digestion efficiency. Furthermore, lactadherin and MUC-1, in addition to the non-glycosylated protein xanthine oxidase, have been shown or suggested in preclinical studies to possess antimicrobial properties.