Degradation mechanism of lignin

Degradation Mechanism of Lignin Model Compounds by Laccase m (16,17)... 

Table I. Degradation Mechanism of Lignin Dimer Models...

Funaoka M, Abe I (1982f) The reaction of lignm under the presence of phenol and boron tnfluoride X The properties of residual lignin and the degradation mechanism of lignin Mokuzai Gakkaishi 28 705-717... 

Following comparison to sound wood (Figs. 5A and 5B), it was clearly evident that degraded wood had undergone oxidation. This oxidative process could take place on both polysaccharides and lignin (22,23), and could therefore represent a general degradation mechanism of the wood cell wall polymers. 

Mechanisms of Lignin Degradation by Lignin Peroxidase and Laccase of White-Rot Fungi... 

S Kawai, T Umezawa, T Fliguchi. Degradation mechanisms of phenolic beta-1 lignin substructure model compounds by laccase of Coriolus versicolor. Arch. Biochem. Biophys. 262(1) 99-110, 1988. 

T Higuchi. Mechanisms of lignin degradation by lignin peroxidase and laccase of white-rot fungi. In NG Lewis, Paice, M.G., eds. Plant Cell Wall Polymers Biogenesis and Biodegradation. ACS Symposium Series, 1989, pp. 482-502. 

The structures of the lignoids 1, 2 and 3 illustrate some common and some different features. All three compounds comprise two C6-C3-moieties, numbered 1 to 9 and V to 9, and hence their monomers are presumably metabolites of the shikimate pathway. Since this pathway is restricted to plants, the biosynthesis of 3 is a mystery. Could enterolactone be a bacterial degradation product of lignins ingested with plant food, or is it synthesized ex novo (133) If so, what are its precursors - a pertinent question since enterolactone lacks oxy-functions at the 4- and 4 -positions of the aryls, a structural particularity not shared with any other naturally occurring C6-C3-dimer known. Indeed free p-hydroxyls are essential for the oxidative coupling of the monomers regardless of the mechanism of the reaction. 

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