Task of plant peroxidases in polychlorinated biphenyls transformation

Function and catalytic mechanism of plant enzymes in transformation of xenobiotics is still not fully explained. Peroxidases are believed to potentially participate in such transformations. With the aim to identify the function of plant peroxidases, crude enzyme extract from Nicotiana tabacum was isolated. To obtain partially purified preparation, proteins of crude extract were precipitated by ammonium sulphate. Partially purified preparation was used in reactions in vitro with various and Structurally different PCB congeners. The sample showed significant activity towards several PCB congeners. The highest conversion (nearly 80 %) was detected with PCB3 and PCB9. Dihydroxy-2,5-dichlorobiphenyl was by GC-MS identified as product of peroxidase reaction with PCB9. During in vitro cultivation of cell cultures of Nicotiana tabacum in presence of PCBs, changes in isoenzyme pattern of peroxidase were detected. Almost all peroxidase isoenzymes were stimulated by exposure to PCBs and some of them were Suppressed. Both separated fractions of peroxidase isoenzymes isolated from tobacco showed the same transformation effectivity to PCB3.