Proteolytic Activity of Some Milk-Clotting Enzymes on κ-Casein

Abstract

Proteolytic activity of some milk-clotting enzymes [calf rennet (chymosin), Mucor miehei rennet, and Cryphonectria parasitica rennet] on κ-casein was determined with reverse-phase HPLC. All enzymes were standardized to the same milk-clotting activity and incubated with κ-casein at 37°C for 1, 5, 15, 30, and 60min. Protein hydrolysis was stopped by addition of 10–5M pepstatin in 8 M urea. Chromatograms of hydrolysis products revealed that the enzymes hydrolyzed κ-casein differently. Chymosin hydrolysis was limited to formation of κ-macropeptide and para-κ-casein; the microbial rennets, particularly that from M. miehei, effected extensive nonspecific hydrolysis of both κ-casein and para-κ-casein.