Endoglucanase (EG) that cleaves the internal beta-1,4-glucosidic bonds in cellulose. Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans. Activity is stimulated by zinc ions, potassium ions and DTT (PubMed:33892036). Activity is inhibited by manganese and chloride ions (PubMed:33892036). Kcat is 129.41/sec for hydrolysis of carboxymethylcellulose (at pH 4.8 and 55 degrees Celsius). Optimum pH is 4.8 (PubMed:33892036). Active from pH 4 to 5 (PubMed:33892036). Activity is significantly reduced at pH 6 and is not observed at pH 7 (PubMed:33892036). Optimum temperature is 70 degrees Celsius (PubMed:33892036). Thermostable (PubMed:33892036). Highly stable at 50, 60 and 70 degrees Celsius (PubMed:33892036). Belongs to the glycosyl hydrolase 5 (cellulase A) family.