PHENOXY RADICAL INTERMEDIATES IN ENZYMATIC DEGRADATION OF LIGNIN MODEL COMPOUNDS

1. 1. Oxidation of monomeric and dimersic syringly derivatives with horseradish peroxidase and H2O2 yielded long-lived phenoxy radicals. These have been fully characterized by electron spin resonance spectrometry. The oxidation reaction proceeded by a sequence of discrete steps, each involving a paramagnetic intermediate. The final step resulted in the clevage of the side chain from the aromatic nucleus to yeild 2,6-dimethoxybenzoquinone. Enzymatic attack was most rapid with alkyl syringly ketones, less rapid with syringly alcohols and slow with syringly alkanes or α-alkoxy ethers. This parallel the concentration of the radical species produced for each compound. A biological clock mechanism appeared to mediate these reactions. 2. 2. The depolymerization of lignin by wood-rotting fungi may result from a series of one-electron steps catalyzed by phenol oxidases. © 1969.