Influence of positioning of carbohydrate binding module on the activity of endoglucanase CelA of Clostridium thermocellum

► Several variants between endoglucanase CelA and the binding module CBM3a were constructed. ► Attachment of the binding module enhanced activity, particularly against insoluble substrates. ► Constructs CelA-BC and CelA-CB with CBM3a attached at N- and C-termini of the catalytic domain, respectively were prepared. ► CelA-BC was more active than CelA-CB. ► The binding residues and the active site residues are more favorably oriented with respect to the substrate in CelA-BC.