An Enzyme Extract from Douglas-Fir Sapwood and Its Relationship To Brown Staining
Keywords:Polyphenol oxidase, Douglas-fir sapwood, chemical stains, brown stains, protein extraction, enzyme activity
AbstractA chemical or enzymatic brown stain in sapwood of Douglas-fir has caused financial losses to lumber producers, particularly those producing valuable clear grades of export lumber. This work shows that the brown stain may be caused, at least in part, by an enzyme system in the sapwood. Buffered extracts of Douglas-fir sapwood showed enzyme activity when added to solutions containing o-diphenol and polyphenol compounds. No activity for monophenol substrates was detected. The enzymatic extract showed two pH optima for activity, one at pH 5.5 and one at pH 8.0, with the activity at pH 8.0 being somewhat greater. The activity was also temperature-dependent, with the highest activity at 35°. The extract showed highest activities with the compounds (—)-epicatechin, dihydroquercetin, and 4-methylcatechol.
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