Purification and characterization of an exoglucanase from Streptomyces flavogriseus

Abstract
S. flavogriseus, a mesophilic actinomycete, produces high levels of extracellular enzymes capable of hydrolyzing cellulose and xylan. One such enzyme, an exoglucanase, was purified to molecular homogeneity by a sequence involving DEAE Bio-Gel A chromatography, gel permeation chromatography on Bio-Gel P-60, preparative isoelectric focusing and concanavalin A affinity chromatography. This purification sequence disclosed the presence of several distinct endoglucanase and xylanase fractions. Homogeneity of the purified enzyme was demonstrated by analytical isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme had a MW of .apprx. 45,000 and an isoelectric point of 4.15. The enzyme demonstrated negligible activity with carboxymethylcellulose as the substrate. It was able to extensively hydrolyze acid-swollen cellulose; the main product of enzyme action was cellobiose.

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