Lignin-degrading enzyme from <i>Phanerochaete chrysosporium</i> : Purification, characterization, and catalytic properties of a unique H ₂ O ₂ -requiring oxygenase

TLDR

An extracellular lignin‑degrading enzyme from *Phanerochaete chrysosporium* was purified to homogeneity by ion‑exchange chromatography. The 42,000‑Da ligninase, containing a single protoheme IX, catalyzes non‑stereospecific oxidations of lignin side chains—including Cα‑Cβ cleavage, benzyl alcohol oxidation, intradiol cleavage, and benzylic hydroxylation—as well as oxidative coupling of phenols, all of which require H₂O₂ while the oxygen atom in substrate oxygenation comes from O₂, making it a unique H₂O₂‑requiring oxygenase.

Abstract

An extracellular lignin-degrading enzyme from the basidiomycete Phanerochaete chrysosporium Burdsall was purified to homogeneity by ion-exchange chromatography. The 42,000-dalton ligninase contains one protoheme IX per molecule. It catalyzes, nonstereospecifically, several oxidations in the alkyl side chains of lignin-related compounds: C α —C β cleavage in lignin-related compounds of the type aryl—C α HOH—C β HR—C γ H 2 OH (R = -aryl or - O -aryl), oxidation of benzyl alcohols to aldehydes or ketones, intradiol cleavage in phenylglycol structures, and hydroxylation of benzylic methylene groups. It also catalyzes oxidative coupling of phenols, perhaps explaining the long-recognized association between phenol oxidation and lignin degradation. All reactions require H 2 O 2 . The C α —C β cleavage and methylene hydroxylation reactions involve substrate oxygenation; the oxygen atom is from O 2 and not H 2 O 2 . Thus the enzyme is an oxygenase, unique in its requirement for H 2 O 2 .