THE NATURE OF THE CELLULOSE-BINDING DOMAIN AFFECTS THE ACTIVITIES OF A BACTERIAL ENDOGLUCANASE ON DIFFERENT FORMS OF CELLULOSE

The cellulose-binding domain (CBD(CenC)) of endoglucanase C (CenC) fro m Cellulomonas fimi binds to amorphous (phosphoric acid-swollen) cellu lose (PASC) but not to bacterial microcrystalline cellulose (BMCC), wh ereas that of endoglucanase A (CBD(CenA)) binds to both forms of cellu lose. Substitution of CBD(CenC) for CBD(CenA) 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 Avice l. The two forms of the enzyme have similar activity on PASC. CenC''A is more active than CenA on cellulose azure and carboxymethyl cellulos e. CenC''A binds to phosphoric acid-swollen cellulose but not to cryst alline 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.