A study on reducing substrates of manganese-oxidizing peroxidases from Pleurotus eryngii and Bjerkandera adusta

A novel peroxidase, oxidizing Mn2+ and different aromatic compounds, was isolated. Hydroquinones, substituted phenols, dl es, other aromatic compounds and Mn2+ were compared as reducing substrates, and conclusions presented in the light of a molecular model built by homology modeling, The enzymes showed the fastest reaction rates with Mn2+, but the highest affinity corresponded to hydroquinones and dyes. Oxidation of Reactive Black 5 (an azo-dye not oxidized by Mn3+) was non-competitively inhibited by Mn2+. These findings, together with identification of putative Mn-binding site (involving Glu(36), Glu(10), Asp(175) and inner heme propionate) and long-range electron transfer pathways, indicate that different sites are involved in substrate oxidation. (C) 1998 Federation of European Biochemical Societies.