The nature of the cellulose-binding domain effects the activities of a bacterial endoglucanase on different forms of cellulose

The cellulose-binding domain (CBDCenC) of endoglucanase C (CenC) from Cellulomonas fimi binds to amorphous (phosphoric acid-swollen) cellulose (PASC) but not to bacterial microcrystalline cellulose (BMCC), whereas that of endoglucanase A (CBDCenA) binds to both forms of cellulose. Substitution of CBDCenC for CBDCenA in endoglucanase A (CenA) affects the activity of the enzyme on different forms of cellulose. The hybrid enzyme (CenC″A) is less active than CenA on BMCC and Avicel. The two forms of the enzyme have similar activity on PASC. CenC″A is more active than CenA on cellulose azure and carboxymethyl cellulose. CenC″A binds to phosphoric acid-swollen cellulose but not to crystalline cellulose. The hybrid enzyme is less sensitive than CenA to C. fimi protease, probably as a consequence of replacement of the prolyl-threonyl linker of CenA by a triprolyl linker from CenC.