Proteolytic activities of some milk clotting enzymes on ovine casein

Proteolytic activity of some milk clotting enzymes (calf and lamb rennets, bovine chymosin and pepsin, and proteases from Rhizomucor miehei and Cryphonectria parasitica) on ovine whole casein was determined by urea-PAGE and RP-HPLC. Microbial enzymes were more proteolytic than animal enzymes when acting on ovine whole casein. Lamb rennet and C. parasitica protease showed the lowest and the highest degree of proteolysis, respectively. Urea-PAGE results showed that all enzymes hydrolyzed ovine casein resulting in the formation of αs1-I and β-I as initial breakdown products of αs1-CN and β-CN. In addition to these products, C. parasitica protease produced a series of degradation products with lower mobilities than β-CN. Minor quantitative differences between coagulants from animal origin, but great quantitative and qualitative differences between microbial and animal coagulants (assessed throughout the study of the RP-HPLC peptide profiles), were observed.