title: Metabolism of hydroxylated PCB congeners by cloned laccase isoforms.
abstract: The white-rot fungus T. versicolor UAMH 8272 produced two groups of laccases, each of which included several isoforms showing different isoelectric points (pI). Group 1 and group 2 laccases, respectively, displayed higher pI 5-6 and lower pI 3-4. Of the four cloned full-length laccase cDNAs, Lac 1 and Lac 4 were expressed in the heterologous protein expression system using Aspergillus oryzae. The measured pI of each Lac 1 and Lac 4 expressed in A. oryzae was lower than that of pI predicted from the amino acid composition. With this regard, isoelectric focusing of Lac 1 showed the presence of multiple protein bands in the 3.0-4.0 pI range, although the predicted pI value of Lac 1 was 4.7. Similarly, Lac 4 exhibited a pI value which was lower than that predicted (3.6 vs. 4.3, respectively). In all tested hydroxyPCBs, higher chlorinated hydroxyPCBs were less susceptible to in vitro degradation by laccase than lower chlorinated hydroxyPCBs. Although Lac 4 showed a generally higher activity than Lac 1, the two laccases were characterized by quite different substrate specificity toward two hydroxy-tetrachlorobiphenyl congeners. Two metabolites were obtained from the metabolism of hydroxy-pentachlorobiphenyl: a ten chlorine-substituted dimer with a C-O bond, and one with a C-C bond.
authors.affiliation: Graduate School of Environmental Health, Azabu University, 1-17-71 Fuchinobe, Sagamihara, Kanagawa, 229-8501, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Fujihiro
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Higuchi
authors.forename: Shin
authors.initials: S
authors.lastname: Hisamatsu
authors.forename: Shigenori
authors.initials: S
authors.lastname: Sonoki
mesh_terms: D001236:Aspergillus oryzae / Q000378:metabolism; D001673:Biodegradation, Environmental; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D007526:Isoelectric Point; D042845:Laccase / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D011078:Polychlorinated Biphenyls / Q000378:metabolism*; D020033:Protein Isoforms; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity; D055454:Trametes / Q000201:enzymology / Q000235:genetics
chemical_list: D005656:Fungal Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D011078:Polychlorinated Biphenyls; D042845:Laccase