Kinetics of chemically modified lignin peroxidase and enzymatic oxidation of aromatic nitrogen-containing compounds

Lignin peroxidase from the white-rot fungus Phanerochaete chrysosporium was chemically modified by reductive alkylation with benzyl, naphthyl and anthracyl moieties, thereby increasing its superficial hydrophobicity. The three chemical modifications altered the kinetic behaviour of the enzyme in 10% acetonitrile with four different substrates: carbazole, pinacyanol, pyrene and veratryl alcohol. Benzyl modification of lignin peroxidase increased the catalytic efficiency (k _cat/K _m,app) 2.7 times for carbazole oxidation. Thirteen N-containing compounds, including pyrroles, pyridines, and aromatic amines, were tested to determine whether they could be oxidized by lignin peroxidase in 10% acetonitrile. All the pyrrole analogues and all the amines tested were oxidized, but none of the pyridine analogous reacted. Some products were isolated and analyzed by high-resolution mass spectrometry. Most were dimers or polymers and, in some cases, these contained oxygen atoms. The possibility of bitumen and petroleum modifications using this enzyme is discussed.