Department of Biochemistry and Biophysics, University of California, Davis 95616.
A Clostridium cellulovorans lambda gt11 gene bank was screened for endo-1,4-beta-glucanase [EC 3.2.1.4, EGase, Carboxy Methyl Cellulase (CMCase)] genes using a chromogenic substrate. Three genes (engA, engB, and engC) were isolated. The engB expressed the most active CMCase. The engA encoded a bifunctional enzyme that displayed endo-1,4-beta-glucanase and beta-glucosidase activities. The three recombinant glucanases, when expressed in Escherichia coli, were partially degraded into multiform active enzymes as evidenced by their SDS-PAGE-CMC zymograms. None of the clones could degrade crystalline cellulose, thus supporting the hypothesis that the integrity of the C. cellulovorans cellulase complex was essential for its 'true cellulase' activity.