A hemoprotein. The enzyme from white rot basidiomycetes is involved in the oxidative degradation of lignin. The enzyme oxidizes a bound Mn2+ ion to Mn3+ in the presence of hydrogen peroxide. The product, Mn3+, is released from the active site in the presence of a chelator (mostly oxalate and malate) that stabilizes it against disproportionation to Mn2+ and insoluble Mn4+ . The complexed Mn3+ ion can diffuse into the lignified cell wall, where it oxidizes phenolic components of lignin and other organic substrates . It is inactive with veratryl alcohol or nonphenolic substrates.
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