Milk-derived peptides effects

Klebsiella pneumoniae infection in mice after intravenous treatment (Meisel and Schlimme, 1996). The mechanism by which milk protein derived peptides exert their immunomodulatory effects is not yet defined. However, opioid peptides may affect the immunoreactivity of lymphocytes via the opiate receptor. There is a remarkable relationship between the immune system and opioid peptides, because opioid p, receptors for endorphins are present on T lymphocytes and human phagocytic leukocytes (Meisel, 1998). 

Paakkari, I., Jarvinen, A., Antila, P., Mattila, M.J., and Pihlanto-Leppala, A. 1994. Opioid effects of the milk whey-protein derived peptides a- and (3-lactorphin. In 3-Casomorphins and Related Peptides. Recent Development (V. Brand and H. Teschemacher, eds), pp. 33-37. VCH, Weinheim. 

Besides being important building blocks in the construction of proteins, some peptides possess their own biological activity. Milk, in particular, is a source of many biologically active peptides. The enzymatic hydrolysis of the milk protein casein releases opioid peptides, which have pharmacological activities such as analgesia and sleep-inducing effects. Other peptides derived from casein are involved in calcium flow in tissues and modification of the immune system response. Other milk peptides... 

Antimicrobial peptides are effective against different bacteria and yeasts. An example of an antimicrobial peptide is lactoferricin, which includes residues 17-41 from lactoferrin. Other peptides with antimicrobial properties are isracidin, derived from casein (residues 1-23), and casocidin-I, as a result of hydrolysis ofa32"Casein (residues 150-188). Lactoferricin also has immuno-and cytomodulatory properties that similarly show a number of peptides arising by hydrolysis of milk caseins and serum proteins. 

Since peptide Al appeared to have been derived from residues 1-16, it was of interest to see whether this peptide, generated in the course of a stopped activation, could inhibit pepsin and the homologous milk-clotting calf protein, chymosin. The results (V. Barkholt Pedersen and P. H. Ward - personal communications) show that Al had no effect on the milk-clotting activity of chymosin (confirming that all of the pepstatin must have been removed) while independently the Danish and American labs produced similar curves for the inactivation of porcine pepsin (Fig.5). Thus, it would seem that the first peptide produced on activation is the inhibitor peptide. This seems to make sense from a control point of view, i.e., the first bond being hydrolyzed on activation releases the pepsin inhibitor so it can exert its effect if required. 

---