Manganese regulation of veratryl alcohol in white rot fungi and its indirect effect on lignin peroxidase

Many white rot fungi are able to produce de novo veratryl alcohol, which is known to be a cofactor involved in the degradation of lignin, lignin model compounds, and xenobiotic pollutants by lignin peroxidase (LIP). In this study, Mn nutrition was shown to strongly influence the endogenous veratryl alcohol levels in the culture fluids of N-deregulated and N-regulated white rot fungi Bjerkandera sp. strain BOS55 and Phanerochaete chrysosporium BKM- F-1767, respectively. Endogenous veratryl alcohol levels as high as 0.75 mM in Bjerkandera sp. strain BOS55 and 2.5 mM in P. chrysosporium were observed under Mn-deficient conditions. In contrast, veratryl alcohol production was dramatically decreased in cultures supplemented with 33 or 264 μM Mn. The LiP titers, which were highest in Mn-deficient media, were shown to parallel the endogenous veratryl alcohol levels, indicating that these two parameters are related. When exogenous veratryl alcohol was added to Mn-sufficient media, high LiP titers were obtained. Consequently, we concluded that Mn does not regulate LiP expression directly. Instead, LiP titers are enhanced by the increased production of veratryl alcohol. The well-known role of veratryl alcohol in protecting LiP from inactivation by physiological levels of H₂O₂ is postulated to be the major reason why LiP is apparently regulated by Mn. Provided that Mn was absent, LiP titers in Bjerkandera sp. strain BOS55 increased with enhanced fungal growth obtained by increasing the nutrient N concentration while veratryl alcohol levels were similar in both N-limited and N-sufficient conditions.