Extracellular protease from culture supernatants of Streptomyces sp. LCJ12A was purified and characterized in this study. The collected supernatant was purified by ammonium sulfate precipitation and DEAE-cellulose chromatography. The molecular weight of the enzyme (20.1 kDa) was determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The culture filtrate, partially purified enzyme and ammonium sulphate precipitate displayed catalysis and stability over pH 311.5 and showed optimal activity at pH 10. The culture filtrate, ammonium sulphate precipitate and partially purified enzyme was good between 30°C 40°C and the optimum temperature was 35°C. The purified protease exhibited high catalytic activity and stability under different pH and temperature. The partially purified protease from Streptomyces sp. LCJ12A showed a substantial relative activity of 78% with BSA, 43% with gelatin and 96% relative activity with casein. The Km and Vmax values for the partially purified protease were calculated from the Lineweaver-Burk plot. The Km values of Streptomyces sp. LCJ12A were 73.5 mM for casein, 44.54 mM for BSA and 43.45 mM for gelatin. The Vmax values were 500 mM min-1 for casein, 303.03 mM min-1 for BSA and 270.27 mM min-1 for gelatin from Streptomyces sp. LCJ12A. The statistical analysis confirmed that compared to the other substrates, casein was significant.
Key words: Alkaline protease, SDS-PAGE, DEAE-Cellulose and Streptomyces sp.
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