Purification and Properties of Proteinase with Optimum pH 6.0 from Gouda-type Cheese

Abstract

The proteinase in Gouda-type cheese, which was ripened for 5 months, was purified by a combination of DEAE-cellulose and Sephadex G-150. The enzyme was purified about 700 fold with a yeild of 5.3%, and showed homogeneity in disc electrophoresis. The enzyme was most active at pH 6.0, and had a temperature optimum at about 30° with a molecular weight of 230, 000. The enzyme was activated by Co²⁺ and Mn²⁺, inhibited by ethylenediaminetetraacetic acid and 1, 10-phenathrolin, and strongly affected by phenylmethylsulfonylfluoride and diisopropyl-fluorophosphate. The enzyme could degrade β-and κ-casein, but had very little effect on α_s1-casein. Since the mobility of the decomposed products from β-casein by the enzyme were similar to those of the breakdown products found in ripening cheese, the enzyme may play an important role in casein breakdown during ripening.