Figure 2

Avicelase activities of the artificial bi-catalytic cellulase and its intramolecular synergy. Shown are activities of artificial bi-catalytic cellulase (uppermost curve), its individual catalytic protein subunits (lowermost two curves), and a simple mixture of the two catalytic subunits (second curve from top). All cellulases were previously complexed with a CBM3a-bearing, single-cohesin scaffoldin binding adaptor, and all were loaded at the same (2.0 μmol/L) concentration, acting against Avicel substrate loaded at 5 g/L, for an enzyme: substrate ratio of 0.4 μmol per g cellulose. Assays were carried out anaerobically at 60°C in 20 mM acetate, pH 5.0, containing 10 mM CaCl₂, 5.0 mM L-cysteine and 2 mM EDTA. In addition to the cellulases under study, each assay mixture included chromatographically purified Aspergillus niger β-glucosidase at a concentration of 0.005 mg/mL (or 1.0 mg/g of cellulose substrate). For key to icons, please see Figure 1 and Table 1.