Purification and Characterization of a Nonylphenol (NP)-degrading Enzyme from Bacillus cereus. Frankland

An extracellular NP-degrading enzyme secreted by Bacillus cereus. Frankland was purified to homogeneity by a combination of ammonium sulfate precipitation, Phenyl-Sepharose hydrophobic-interaction chromatography and DEAE anion-exchange chromatography. On SDS (sodium dodecyl sulfate)-polyacrylamide gel electrophoresis analysis, the purified enzyme showed a relative molecular mass of 58.3 kDa. The depolymerzation of sub-units was accompanied with the loss of NP-degrading enzyme activity, and removing denaturing factors by dialysis could restore the dimer structure and enzymatic activity. The enzyme had an isoelectric point of 5.5 and an optimal temperature of 60 degrees C, and was the most active at pH 6.0. The enzymatic activity was stable at pH 4-8 and inhibited by Cu2+. Ten N-terminal amino acids were determined to be ASVNSIKIGY, demonstrating that the purified enzyme was a novel one. The hydrolysis pattern of the purified enzyme indicated that the NP-degrading enzyme was an endo NP-degrading enzyme. The extraordinary thermo-stability provided the enzyme with a good prospect to be used as a new tool for clean-production process for textile industry.