Xylanase Activity of an Endo-Cellulase of Carboxymethyl-Cellulase Type from Irpex lacteus [Polyporus tulipiferae)

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Abstract
An endo-cellulase [EC 3.2.1.4] of carboxymethyl-cellulase type (F-1) which was fractionated from culture filtrate of Irpex lacteus and purified to electrophoretic and ultracentrifugal homogeneity, was found to show xylanase [EC 3.2.1.8] activity. The activity was not removed from any of the intermediate fractions during the purification of the initial F-I peak, and the ratio of xylanase to cellulase activity remained almost unchanged through the purification processes. The xylanase activity of F-l showed not only the same optimal pH, heat stability, and pH stability as its cellulase activity, but also the same mobility as the cellulase activity upon cellulose acetate film and starch zone electrophoreses. The overall rates of hydrolysis of mixtures of various concentrations of CM-cellulose and xylan by F-l coincided well with those calculated from the Michaelis-Menten treatment of two substrates competing for the same active site of the enzyme. These results indicate that the xylanase activity of F-l is intrinsic to the cellulase itself.

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