CELLULOSE-BINDING DOMAINS CONFER AN ENHANCED ACTIVITY AGAINST INSOLUBLE CELLULOSE TO RUMINOCOCCUS-ALBUS ENDOGLUCANASE-IV

The gene encoding cellulose-binding domains (CBDs) from Clostridium st ercorarium xylanase A was joined to the egIV gene encoding endoglucana se IV (EGIV) from Ruminococcus albus. The hybrid protein (EGIV + CBD) expressed from this fusion gene in Escherichia coli acquired the abili ty to adsorb onto insoluble celluloses such as ball-milled cellulose ( BMC). EGIV + CBD was more active toward BMC at low concentrations than the parental enzyme, EGIV, although there was no difference in the ca talytic properties between them toward carboxymethyl cellulose. This r esult indicates that the addition of the CBDs to EGIV enhances enzyme activity on the insoluble cellulose by concentrating the catalytic dom ain on the substrate surface.