Studies on the Biosynthesis of Lignin

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Abstract
Latex of the Japanese lacquer tree was found to contain a phenolase [EC 1.10.3.1] and a peroxidase [EC 1.11.1.7] in addition to laccase [EC 1. 10.3.2], and the three enzymes were separated from one another. Laccase was purified to a homogeneous state and shown to be incapable of catalyzing the aerobic oxidation of coniferyl alcohol. The phenolase separated from the latex could oxidize coniferyl alcohol, though it contained little contaminating peroxidase. The peroxidase obtained from the latex, like wheat germ peroxidase 556, could catalyze active oxidation of coniferyl alcohol in the presence of hydrogen peroxide; the activity could be detected even with low concentrations of hydrogen peroxide and coniferyl alcohol. The formation of a lignin-like dehydrogenative polymerization product from coniferyl alcohol by the action of phenolase and peroxidase could be detected by measuring increases in turbidity and also by changes in absorption spectrum of the reaction mixtures. The formation of the polymerization product was much faster with peIoxidase than with phenolase. It was concluded that the oxidation of coniferyl alcohol by the crude latex extract was due to the action of phenolase but not to that of laccase.

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