This enzyme catalyzes the endohydrolysis of 1,4-beta-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans. Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans. In the N-terminal section; belongs to the glycosyl hydrolase 5 (cellulase A) family. In the C-terminal section; belongs to the glycosyl hydrolase 26 family.