Mechanism of substrate hydrolysis by a thermophilic endoglucanase from Thermotoga maritima

A cellulase from the thermophile, Thermotoga maritima, hydrolyzed oligosacc haride substrates by an exoglucanase mode of action but acted as an endoglu canase to rapidly reduce the Viscosity of the soluble polysaccharides carbo xymethylcellulose and barley beta-glucan. The V-max for hydrolysis of the s ubstrate, p-nitrophenyl beta-D-cellobioside, was 42 mu mol min(-1) (mg prot ein)(-1), while that for barley beta-glucan was 637. The enzyme had little activity on crystalline cellulose.