Unique Structural Features of the Peptidoglycan ofMycobacterium leprae

Publisher Website
Google Scholar
Abstract
The peptidoglycan structure ofMycobacteriumspp. has been investigated primarily with the readily cultivableMycobacterium smegmatisandMycobacterium tuberculosisand has been shown to contain unusual features, including the occurrence of N-glycolylated, in addition to N-acetylated, muramic acid residues and direct cross-linkage betweenmeso-diaminopimelic acid residues. Based on results from earlier studies, peptidoglycan from in vivo-derived noncultivableMycobacterium lepraewas assumed to possess the basic structural features of peptidoglycans from other mycobacteria, other than the reported replacement ofl-alanine by glycine in the peptide side chains. In the present study, we have analyzed the structure ofM. lepraepeptidoglycan in detail by combined liquid chromatography and mass spectrometry. In contrast to earlier reports, and to the peptidoglycans inM. tuberculosisandM. smegmatis, the muramic acid residues ofM. lepraepeptidoglycan are exclusively N acetylated. The un-cross-linked peptide side chains ofM. lepraeconsist of tetra- and tripeptides, some of which contain additional glycine residues. Based on these findings and genome comparisons, it can be concluded that the massive genome decay inM. lepraedoes not markedly affect the peptidoglycan biosynthesis pathway, with the exception of the nonfunctionalnamHgene responsible forN-glycolylmuramic acid biosynthesis.