An enzyme synthesising salidroside with p-tyrosol and P-D-glucose was isolated from Aspergillas niger, purified and characterized in this paper. After (NH4)(2)SO4 precipitation and ion exchange chromatography, the enzyme was purified to one band in SDS-polyacrylamide gel electrophoresis, and its molecular weight was about 84.6 kDa. The optimum temperature of the enzyme was 45 degrees C, and the optimum pH was 5.0. The enzyme was stable at less than 55 degrees C and pH 4.5-6.0. The enzyme catalyzed p-tyrosol and P-D-glucose to form salidroside in the concentrations of 1.5% p-tyrosol and 6% P-D-glucose. The yield of salidroside was about 10%. (c) 2005 Elsevier Ltd. All rights reserved.