Endolysin involved in host peptidoglycan digestion after permeabilization of the cytoplasmic membrane by holin. Involved in host cell lysis and liberation of progeny phages. Displays strong lytic activity against chloroform-treated Gram-negative cells. Hydrolysis of (1->4)-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrins. Optimum pH is 7.0-8.0. Inactivation temperature above 4 degrees Celsius. May be associated with the viral membrane via P20 and P22. Belongs to the glycosyl hydrolase 24 family.