Specificity of milk-clotting enzymes towards bovine kappa-casein

Limited proteolysis of bovine kappa-casein has been investigated with porcine pepsin A and C, and with the 2 microbial proteinases Mucor miehei proteinase and Endothia parasitica proteinase. The liberated C-terminal glycomacropeptide of kappa-casein was isolated after precipitation in 3% trichloroacetic acid followed by high-performance gel-permeation chromatography on a TSK G3000 SW column. From amino acid analyses and N-terminal sequencing of the liberated peptide it is concluded that porcine pepsin A, C and Mucor miehei proteinase cleave the same bond as chymosin: Phe-105-Met-106 whereas Endothia parasitica proteinase cleaves the bond Ser-104-Phe-105.