Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans. A short form (EG-A-S) arises from post-translational proteolysis of approximately 150 AA at the C-terminus of EG-A-L. Belongs to the glycosyl hydrolase 44 (cellulase J) family.