酵母で熟成されるチーズに関する研究-3-Saccharomyces fragilisの菌体内蛋白分解酵素の分離精製および性質

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Proteolytic enzymes in cell autolysate of Saccharomyces fragilis, which was used for the manufacture of yeast ripened semi-soft cheese, were purified with the method of ethanol fractionation, gel filtration with Sephadex G-75 and DEAE-Sephadex A-50 chromatography, and some of their properties were investigated.Proteolytic activity in cell autolysate was recovered completely by precipitation with ethanol and the specific activity was increased by 8 times. Further purification by gel filtration resulted in the increase of specific activity by 24 times of that of autolysate.This enzyme preparation was fractionated into three active fractions (Protease I, II and III) with DEAE-Sephadex A-50 chromatography. The specific activities of Protease I, II and III were 42, 75 and 67 times respectively, of that for cell autolysate.Although the optimum pH for Protease I and II was 9.0, more than 50% of the activity remained at pH5.5-6.5 (the pH of yeast ripened cheese). Protease III had its optimum pH at 3.0, but it also remained more than 70% of maximum activity at pH5. 5-6.5. All of these three kinds of protease produced by S. fragilis could take part in the ripening of yeast ripenedsemi-soft cheese.Protease I, II and III were inhibited with PCMB (10-3M) and DFP(_??_10-3M). EDTA (10-3M) had no effect on their proteolytic activity.
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