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. Glycan metabolism; cellulose degradation. The signal sequence was not cleaved in the protein expressed in E.coli. Belongs to the glycosyl hydrolase 5 (cellulase A) family.