Exolysin are viral lytic enzymes allowing digestion of bacterial cell wall upon virus entry. This activity is necessary for the virus to reach the host plasma membrane and inject its DNA in the host cytoplasm. The degradation is local, the virion drills a hole large enough to have its tail or capsid pass the wall.
Depending on the enzymatic specificity, exolysins are divided into five main classes.
| Virus | family | Host bacteria | phage enzyme | ref. |
| Phage GA-1 | Podoviridae | Bacillus G1R | gp3 |  |
| Phage SPβ | Siphoviridae | Bacillus subtilis | YomI | |
| Phage SPO1 | Myoviridae | Bacillus subtilis | - | |
| Phage SPP1 | Siphoviridae | Bacillus subtilis | - | |
| Phage M2 | Podoviridae | Bacillus subtilis | gp3 | |
| Phage φ29 | Podoviridae | Bacillus subtilis | gp3 | |
| Phage PRD1 | Tectiviridae | Escherichia coli | p7 | |
| Phage T3 | Podoviridae | Escherichia coli | gp16 | |
| Phage K1-5 | Podoviridae | Escherichia coli | orf35 | |
| Phage N4 | Podoviridae | Escherichia coli | - | |
| Phage T4 | Podoviridae | Escherichia coli | gp5 | |
| Phage T5 | Siphoviridae | Escherichia coli | Pb2 | |
| Phage C1 | Podoviridae | Escherichia coli | - | |
| Phage φ949 | Unclassified | Lactococcus lactis | - | |
| Phage φ31 | Siphoviridae | Lactococcus lactis | - | |
| Phage φc2 | Myoviridae | Lactococcus lactis | - | |
| Phage φr1t | Unclassified | Lactococcus lactis | - | |
| Phage φ6 | Cystoviridae | Pseudomonas syringae | P5 | |
| Phage φ13 | Cystoviridae | Pseudomonas syringae | - | |
| Phage SP6 | Podoviridae | Salmonella typhimurium | orf35 | |
| Phage φP22 | Podoviridae | Salmonella typhimurium | gp4 | |
| Phage φYeO3-12 | Podoviridae | Yersinia enterocolitica | gp16 | |
| Phage φKMV | Podoviridae | Pseudomonas aeruginosa | gp36 | |
| Phage φKZ | Myoviridae | Pseudomonas aeruginosa | gp181 | |
| Phage T7 | Podoviridae | Escherichia coli | gp16 | |