Proteolytic Activity of Some Proteinases on Macropeptides Isolated from κ-casein
Journal of Dairy Science
Proteolytic activities of chymosin, bovine pepsin, Mucor miehei rennet, Cryphonectria parasitica (formerly Endothia parsitica) rennet, trypsin, and Chymotrypsin on κ-casein macropeptide were measured. Macropeptide solutions (10 mg/ml of .05 M, pH 6.6 phosphate buffer) were incubated with the enzymes at 37°C for various times, and their reactions were stopped by adding .025 ml of pepstatin (1 mg/ml of methanol). Peptides released from κ-casein macropeptide were then fractionated using reverse-phase HPLC. At the pH of milk (pH 6.6). κ-casein macropeptide was resistant to enzymic action by chymosin, bovine pepsin, and M. miehei and C. parasitica rennets. Bovine pepsin hydrolyzed κ-casein macropeptide at pH 3. κ-Casein macropeptide was readily hydrolyzed at pH 6.6 by trypsin and chymotrypsin. Possible physiological functions of the κ-casein macropeptide are discussed in light of these findings.
Shammet, K.M., Brown, R.J. and D.J. McMahon. 1992. Proteolytic activity of some proteinases on macropeptides isolated from κ-casein J. Dairy Sci. 75:1380-1388.