Human milk is known to contain several proteases, but little is known about whether these enzymes are active, which proteins they cleave and their relative contribution to milk protein digestion in vivo. In this publication founder Nora Khaldi and co-authors show that several enzymes are actively taking part in the digestion of human milk proteins within the mammary gland, including plasmin and/or trypsin, elastase, cathepsin D, pepsin, chymotrypsin, a glutamyl endopeptidase-like enzyme and proline endopeptidase. Two proteins were most affected by enzyme hydrolysis: β-casein and polymeric immunoglobulin receptor. In contrast, other highly abundant milk proteins such as α-lactalbumin and lactoferrin appear to have undergone no proteolytic cleavage.
You can obtain the paper at the Journal of Dairy Science following link http://pubs.acs.org/doi/abs/10.1021/jf405601e
Khaldi, N.; Vijayakumar, V.; Dallas, D. C.; Guerrero, A.; Wickramasinghe, S.; Smilowitz, J. T.; Medrano, J. F.; Lebrilla, C. B.; Shields, D. C.; German, J. B., Predicting the important enzyme players in human breast milk digestion. J Agric Food Chem 2014.