Purification, biochemical characterisation and mode of action of an extracellular endo-dextranase from the culture filtrate of Penicillium lilacinum

An extracellular endo-dextranase had been purified from the culture filtrate of Penicillium lilacinum by calcium phosphate gel chromatography. The homogeneity of the purified protein with dextranase activity was established by polyacrylamide gel electrophoresis. Size-exclusion HPLC and sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis indicated that the enzyme had a molecular mass of approx. 26,500 +/- 1500. The rapid fall in viscosity and identification of major hydrolysis products of dextran (i.e. isomaltose, isomaltotriose, isomaltotetraose and glucose) by the purified dextranase (Fraction III) indicated that the enzyme was an endodextranase. The K-m value of the purified dextranase was 0.06 mu g/ml indicating that the enzyme had a very high specificity for dextran.