Comparative catalytic activity of two plant proteinases upon caprine caseins in solution

The proteolytic activities of cardosins A and B, two (plant) proteinases from Cynara cardunculus, toward caprine caseins, independently, or in the presence of each other as Na-caseinate, were studied in a comparative fashion using polyacrylamide gel electrophoresis and reversed phase high performance liquid chromatography. The electrophoretic degradation patterns of both αs- and β-casein, brought about by the cardosins, were similar to one another. In what concerns the specificity of these two enzymes upon caseinate, the major cleavage sites were Leu127-Thr128 and Leu190-Tyr191, both in β-casein. When caseins were tested independently, both cardosins cleaved Phe153-Tyr154 in αs1-casein, as well as Leu127-Thr128 and Leu190-Tyr191 in β-casein.