Purification and characterization of two novel peroxidases from the dye-decolorizing fungus Bjerkandera adusta strain CX-9

Two extracellular peroxidases from Bjerkandera adusta strain CX-9, namely a lignin peroxidase (called LiP BA45) and manganese peroxidase (called MnP BA30), were purified simultaneously by applying successively, ammonium sulfate precipitation-dialysis, Mono-S Sepharose anion-exchange and Sephacryl S-200 gel filtration and biochemically characterized. The sequence of their NH2-terminal amino acid residues showed high homology with those of fungi peroxidases. Matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) analysis revealed that the purified enzymes MnP BA30 and LiP BA45 were a monomers with a molecular masses 30125.16 and 45221.10 Da, respectively. While MnP BA30 was optimally active at pH 3 and 70 °C, LiP BA45 showed optimum activity at pH 4 and 50 °C. The two enzymes were inhibited by sodium azide and potassium cyanide, suggesting the presence of heme-components in their tertiary structures. The Km and Vmax for LiP BA45 toward 2,4-Dichlorolphenol (2,4-DCP) were 0.099 mM and 9.12 U/mg, respectively and for MnP BA30 toward 2,6-Dimethylphenol (2,6-DMP), they were 0.151 mM and 18.60 U/mg, respectively. Interestingly, MnP BA30 and LiP BA45 demonstrated higher catalytic efficiency than that of other tested peroxidases (MnP, LiP, HaP4, and LiP-SN) and marked organic solvent-stability and dye-decolorization efficiency. Data suggest that these peroxidases may be considered as potential candidates for future applications in distaining synthetic-dyes.