ACTIVITY AND THERMOSTABILITY OF CARBOXYMETHYLCELLULASE FROM ASPERGILLUS-NIGER IS STRONGLY INFLUENCED BY NONCOVALENTLY ATTACHED POLYSACCHARIDES

Removal of non-covalently attached polysaccharides from carboxymethylc ellulase (CMCase) of Aspergillus niger improved its activity but decre ased its thermostability and protease resistance, The activation energ y profile of the hydrolysis of carboxymethylcellulose (CMC) was tripha sic with increasing values of 17, -55 and -562 kJ/mol for polysacchari de-free and 19, -21 and -207 kJ/mol for polysaccharide-complexed CMCas e. The specificity constant (V-max/K-m) of polysaccharide-free CMCase was 1.41 compared to polysaccharide-complexed CMCase which was only 0. 68. The polysaccharide free CMCase had lower thermostability ('melting point' = 82 degrees C) and higher protease susceptibility compared to polysaccharide-complexed CMCase ('melting point' > 100 degrees C).