Lignin-degrading enzyme from Phanerochaete chrysosporium: Purification, characterization, and catalytic properties of a unique H(2)O(2)-requiring oxygenase |
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| Authors: | Tien M Kirk T K |
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| Affiliation: | Forest Products Laboratory, U.S. Department of Agriculture, Forest Service, Madison, WI 53705. |
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| 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: Cα—Cβ cleavage in lignin-related compounds of the type aryl—CαHOH—CβHR—CγH2OH (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 H2O2. The Cα—Cβ cleavage and methylene hydroxylation reactions involve substrate oxygenation; the oxygen atom is from O2 and not H2O2. Thus the enzyme is an oxygenase, unique in its requirement for H2O2. |
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