Novel endopeptidase overcoming lysostaphin resistance

This study reports the discovery and characterization of a novel enzyme, LssR, a member of the M23 family of peptidoglycan hydrolases from Staphylococcus simulans. Three variants of LssR: the full-length protein (LssR_FL), the mature form (LssR_M), and the catalytic domain (LssR_CD) were cloned, overexpressed in a heterologous E. coli system, and purified. The bacteriolytic activities of these variants were systematically evaluated, and optimal conditions were established for each of them. Notably, all variants exhibited robust bacteriolytic activity against live staphylococcal cells, including strains with serine-containing cross-bridges, that typically confer resistance to lysostaphin. To our knowledge, this is the first report of a novel endopeptidase cleaving serine-containing cross-bridges in staphylococcal peptidoglycan, underscoring potential of LssR as a promising antimicrobial agent capable of overcoming possible lysostaphin resistance.