Purification and Properties of Proteinase with an Optimum pH at 8.0 from Gouda-Type Cheese and Its Comparison with Milk Proteinase

Abstract

The proteinase was purified from Gouda-type cheese by combination of ammonium sulfate fractionation, and CM-Sephadex and DEAE-cellulose chromatographies. The purified enzyme exhibited homogeneity in disc electrophoresis, and was most active at pH 8.0.Diisopropyl-fluorophosphate inactivated the enzyme, which was also inhibited by N-α-tosyl-L-lysine-chloromethylketone and soybean trypsin inhibitor. The molecular weight of the enzyme was 100, 000. Several fragments were generated by treating α_s1-casein with the enzyme. The decomposed products of β-casein by the enzyme had an equal mobility to γ-casein (β-CN (f 29-209), β-CN (f 106-269) and β-CN (f 109-209)).These properties of the enzyme were similar to those of alkaline proteinase in milk, and therefore, the enzyme is regarded as alkaline proteinase in milk.