Isolation, Purification, And Characterization Of Some Cystein Proteases From Bovine Mastites Milk

Abstract

Proteolytic activity of cysteine proteases were studied in bovine mastitis milk, four fractions designated as F1,F2,F3,F4 with cysteine protease activity were separated from leukocytes cell by ion- exchange Chromatography through DEAE-Cellulose The most active fraction F4 was selected for further purification utilizing gel filtration Chromatography on Sephadex G-100 column it has been found that F4 most likely being cathepsin B. purification folds and the enzyme yield was 46.66 and 31.81% respectively . polyacrylamide gel electrophoresis test indicated that the enzyme has been purified to homogeneity by giving a single band . The results of enzyme characterization showed that the molecular weights were 31000 and 30000 Daltons as determined by gel filtration and electrophoresis methods in present of reducing agent SDS- PAGE respectively. The optimum pH for the enzyme activity was 6.0 and it was stable at pH values ranged between 4.5 - 6.5. The enzyme exhibited the maximum activity at 45ºC and the enzyme retained its entire activity over 30 min incubation at 30 -50 C and it retained (50, 20, 10) % of its entire activites over 30 min incubation at (60, 70, 80) C respectively. From this results and results observed from the effect of inhibitor and activator reagents we suggest that enzyme F4 possibly belonged to cathepsin B.