Proteolytic Activity of Some Proteinases on Macropeptides Isolated from κ-casein

Document Type

Article

Journal/Book Title/Conference

Journal of Dairy Science

Issue

75

Publication Date

1992

First Page

1380

Last Page

1388

Abstract

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.

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