PG units and chemical bonds associated with remodelling enzyme activities. At the top and bottom of the figure are shown the NAG-NA/GM sugar backbone in anti-parallel orientation. The NAM residues are designated as NA/GM to correspond to the N-glycolylation of muramic acid in mycobacteria. Enzymatic activities are indicated by arrows: Rpfs [yellow], PBPs [orange], endopeptidases [pink], L,D-transpeptidases [green] and amidases [blue], which are related to the corresponding colours in Table 1. Amino acid residues in the stem peptide are shown in black text. Pentapeptide stems are attached to the Carbon at position 3 of the NAM ring. Transglycosylase activities of Rpfs and the Pon domain indicate their ß-1,4-glycosidic bond substrate. Synthetic enzyme activities are shown on the left, that is those that generate bonds cross-linking the pentapeptides on opposing stems, by Pon and Pbp proteins at positions 4,3 (L-Ala to meso-DAP) or Ldt proteins at positions 3,3 (meso-DAP to meso-DAP). The hydrolytic enzyme activities are shown to the right. These include the amidases, the RipA endopeptidases and the DD-CPase (DacB) acting on the pentapeptide stem (pre- or post-crosslinking).
Machowski et al. BMC Microbiology 2014 14:75 doi:10.1186/1471-2180-14-75