Studies on Microbial Levanase

Part II. Purification and properties of the enzyme from Streptomyces griceus

Abstract

An enzyme levanase (levan depolymerase) from a strain of Streptomyces griseus was purified. The enzyme in cultivation broth was concentrated about 300 times through the treatments such as DEAE-Sephadex adsorption, salting out with ammonium sulphate and gel filtration with Biogel. Purity of the enzyme was certified from the results of polyacrylamide-gel electrophoresis and sedimentation pattern of ultracentrifuge.
The optimum reaction temperature was about 50°C and the enzyme was stable at temperatures under 50°C. pH optimum of the reaction was observed to be at 6.5 and pH stability was found at pH 6-8. The enzyme was reactive on levan produced by B. subtilis, but not on sucrose, raffinose, inulin and dextran. The enzyme reaction was inhibited by the presence of the materials such as pCMB, Cu, Ni, Mn, and Zn ions, especially by pCMB and Cu. On the other hand, the presence of Mg ion was found to activate the reaction.
Michaelis constant was calculated as 0.0073g/ml. Molecular weight of the enzyme estimated by gel filtration was 45000 and its sedimentation coefficient (S20.w) was calculated to be 4.75S.