Proteolytic activities of chymosin and porcine pepsin on buffalo, cow, and goat whole and β-casein fractions

The proteolytic specificity and activity of a recombinant chymosin (Maxiren) and porcine pepsin on buffalo, cow, and goat whole casein (CN) and beta-CN were studied by analyzing the degradation products. The results suggest that the hydrolysis of whole casein of buffalo and goat by chymosin was similar to that of cow casein resulting in alpha(s1)-I and beta-I, -II, and -III as degradation fragments of alpha(s1)- and beta-CN. The exception was goat beta-I which was resistant to further hydrolysis by chymosin but not to porcine pepsin at pH 5.4-6.2. Increasing NaCl concentration to greater than or equal to 5% reduced the proteolysis of beta-CN in all three species, but not that of alpha(s1)-CN. The fragments of beta-I, -II, and -III produced from beta-CN of the three species gave identical results with PAGE. alpha(s1)-I and its degradation fragments had in all three species, regardless of the different electrophoretic mobilities on PAGE, the same sequence of appearance. The results indicate that chymosin and porcine pepsin attacked in buffalo and goat caseins the same regions as known for cow alpha(s1)- and beta-CN.