The purification and properties of (1→4)-β-D-glucan cellobiohydrolase from Sclerotium rolfsii: substrate specificity and mode of action

Abstract

A cellulolytic enzyme which shows high activity towards H3PO4 – swollen cellulose, but no viscosity-lowering activity towards carboxymethylcellulose, has been purified from the culture filtrates of Sclerotium rolfsii. The purified enzyme is homogeneous in disc gel electrophoresis, with and without sodium dodecyl sulfate, and in analytical isoelectric focusing in polyacrylamide gel. The enzyme is a glycoprotein containing 7.0% total carbohydrate and has a relative mass of 41 500 and an isoelectric point of 4.32. The enzyme is composed of a single polypeptide chain and has no cystine or half-cystine residues. It is specific for β-D-(1→4)-linkage. The principal product from each of the substrate was cellobiose (93–96%); glucose was also detected (4–7%). The rate of cellodextrin hydrolysis increased as the degree of polymerization increased. The enzyme has been identified as (1→4)-β-D-glucan cellobiohydrolase. The enzyme does not show transglycosylase or transferase activity.