Protective effect of milk peptides: antibacterial and antitumor properties.

There is no doubt that milk proteins provide excellent nutrition for the suckling. However, apart from that, milk proteins can also exert numerous physiological activities benefiting the suckling in a variety of ways. These activities include enhancement of immune function, defense against pathogenic bacteria, viruses, and yeasts, and development of the gut and its functions. Besides the naturally occurring, biologically active proteins present in milk, a variety of bioactive peptides are encrypted within the sequence of milk proteins that are released upon suitable hydrolysis of the precursor protein. A large range of bioactivities has been reported for milk protein components, with some showing more than one kind of biological activity (Korhonen & Pihlanto, 2006). This chapter reviews the most important antimicrobial and antitumor peptides derived from milk proteins, especially those that may have a physiological significance to the suckling neonate. Antimicrobial peptides present in milk that are not derived from milk proteins are also considered. Special attention is given to the generation of these peptides by the action of different proteolytic enzymes and the origin of these enzymes since, if present in the digestive tract, it is likely that the peptides might play a role in the host defense system. Finally, the most relevant in vivo studies carried out with this kind of bioactive peptides are discussed.