LytN is a YSIRK-G/S-signal-peptide protein delivered to the cross-wall (septal) compartment, and its CHAP domain functions as both an N-acetylmuramoyl-L-alanine amidase and a D-alanyl-glycine endopeptidase; catalysis depends on Cys266 and His329.

lytN mutations cause structural damage to the cross-wall and impair staphylococcal growth, while overexpression triggers cross-wall rupture; the phenotype is reversed by controlled lytN expression but not by externally added purified LytN, indicating that correct cross-wall targeting is required.

LytN, a cross-wall murein hydrolase, contributes to the release of protein A by removing amino sugars (MurNAc-GlcNAc) from attached peptidoglycan; however, mutants lacking cross-wall hydrolases (Atl, Sle1, or LytN) released protein A with altered peptidoglycan structures without affecting the overall release of protein A.

LytN is classed among the S. aureus peptidoglycan hydrolases with both amidase and endopeptidase activities, and wall teichoic acid together with the YSIRK/GS signal peptide mediates its localization to the cross-wall of the septum.

LytN is cited as the only other recognised S. aureus D-Ala-Gly hydrolase; its CHAP domain cleaves both D-Ala-Gly and MurNAc-L-Ala bonds, i.e. it is a D-alanyl-glycine endopeptidase as well as an N-acetylmuramoyl-L-alanine amidase.

Review noting CHAP as a frequent catalytic motif and LysM as a common cell-wall-binding motif in cell-wall-active enzymes; disruption of LytN causes growth and morphology defects while overexpression causes lysis and death.