Hybrid Mn-peroxidase from the ligninolytic fungus Panus tigrinus 8/18. Isolation, substrate specificity, and catalytic cycle

Abstract

Increased manganese concentration during submerged cultivation of the ligninolytic white rot fungus Panus tigrinus 8/18 on N-limited mineral medium resulted in the induction of Mn-peroxidase and laccase. The Mn-peroxidase was purified with the purity factor RZ (A(406)/A(280)) = 4.3. The purified enzyme catalyzed H2O2-dependent oxidation of phenol oxidase substrates (aromatic amines, 2,2;-azinobis-(3-ethylbenzthiazolinesulfonic acid), hydroquinone, 2,6-dimethoxyphenol) without Mn2+, which is not typical for the usual Mn-peroxidases. Guaiacol and 2,4,6-trichlorophenol were not oxidized in the absence of Mn2+. Study of absorption spectra of the intermediates of the catalytic cycle revealed that this peroxidase is able to complete the redox cycle, reducing one-electron oxidized intermediate (Compound II) by Mn2+, as well as by an organic substrate (hydroquinone). This means that the enzyme is a "hybrid" Mn-peroxidase, different from the common Mn-peroxidases from ligninolytic fungi.