Medullasin modifies the functions of natural killer cells, monocytes and granulocytes. Inhibits C5a-dependent neutrophil enzyme release and chemotaxis (By similarity). Capable of killing E.coli; probably digests outer membrane protein A (ompA) in E.coli (PubMed:10947984). Hydrolysis of proteins, including elastin. Preferential cleavage: Val-|-Xaa > Ala-|-Xaa. Interacts with NOTCH2NL. Mice with a homozygous knockout of this gene are more easily killed by wild-type E.coli, but the knockout has no visible killing effect on E.coli deleted for outer membrane protein A (ompA). Belongs to the peptidase S1 family. Elastase subfamily.