Purification and characterization of a dimethoate-degrading enzyme of Aspergillus niger ZHY256, isolated from sewage

A dimethoate-degrading enzyme from Aspergillus niger ZHY256 was purified to homogeneity with a specific activity of 227.6 U/mg of protein. The molecular mass of the purified enzyme was estimated to be 66 kDa by get filtration and 67 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point was found to be 5.4, and the enzyme activity was optimal at 50 degreesC and pH 7.0. The activity was inhibited by most of the metal ions and reagents, while it was induced by Cu2+. The Michaelis constant (K-m) and V-max for dimethoate were 1.25 mM and 292 mu mol min(-1) mg of protein(-1), respectively.