Nonphenolic
β-O-4 lignin substructure model dimer, 1,3-dihydroxy-2-(2,6-dimethoxyphenoxy)-1-(4-ethoxy-3-methoxyphenyl)propane (
I) was degraded by horseradish peroxidase (HRP) in the presence of hydrogen peroxide and 1-hydroxybenztriazole (HBT). 4-Ethoxy-3-methoxybenzoic
acid (
II), 1-(4-ethoxy-3-methoxyphenyl)-3-hydroxypropanone (
III), 2,3-dihydroxy-1-(4-ethoxy-3-methoxyphenyl)-1-formyloxypropane (
IV), 2,3-dihydroxy-1-(4-ethoxy-3-methoxyphenyl)propanone (
V), 1-(4-ethoxy-3-methoxyphenyl)-1,2,3-trihydroxypropane (
VI), 1-(4-ethoxy-3-methoxyphenyl)-1,2,3-trihydroxypropane-2,3-cyclic carbonate (
VII), and 1-(4-ethoxy-3-methoxyphenyl)-1,2,3-trihydroxypropane-1,2-cyclic carbonate (
VIII) were identified as degradation products by gas chromatography-mass spectrometry. These degradation products were qualitatively
the same as those of substrate
I in the laccase/HBT system, but the yield of the products was apparently different. The products catalyzed by the HRP/H
2O
2/HBT system contained large amounts of the aromatic ring cleavage products
IV, VII, and
VIII compared with those catalyzed by the laccase/HBT system, while the amount of C
α-C
β cleavage product
II is relatively low. These results suggest that the role of HBT is not in a simple one-electron transfer between the enzymes
and substrates.
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