Analysis of a cellodextrinase cloned from Ruminococcus flavefaciens FD-1

Abstract A cellulase gene from Ruminococcus flavefaciens FD-1 had previously been cloned in Escherichia coli . The product of this gene, CelA, was purified from E. coli and characterised. This 39 kDa cellulase is antigenically related, and of similar mass, to a protein in R. flavefaciens . The enzyme has cellodextrinase activity with predominantly exo-type action. CelA activity was optimal at pH 6.5 and 41°C, and was inhibited in the presence of divalent metal cations. The K _m and V _max were determined as 0.68 mM and 1.89 μmol min⁻¹ mg⁻¹ of CelA, respectively. Cellobiose was the major end product of cellodextrin hydrolysis, and our results suggest that celluboise is competitive inhibitor of CelA.