Open AccessAn Anhydro- N -Acetylmuramyl- l -Alanine Amidase with Broad Specificity Tethered to the Outer Membrane of Escherichia coli
Author(s) -
Tsuyoshi Uehara,
James T. Park
Publication year - 2007
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00446-07
Subject(s) - amidase , periplasmic space , escherichia coli , biology , alanine , biochemistry , peptidoglycan , bacterial outer membrane , mutant , cytoplasm , amino acid , peptide sequence , enterobacteriaceae , bacterial cell structure , peptide bond , enzyme , microbiology and biotechnology , bacteria , gene , genetics
From its amino acid sequence homology with AmpD, we recognized YbjR, now renamed AmiD, as a possible second 1,6-anhydro-N -acetylmuramic acid (anhMurNAc)-l -alanine amidase inEscherichia coli . We have now confirmed that AmiD is an anhMurNAc-l -Ala amidase and demonstrated that AmpD and AmiD are the only enzymes present inE. coli that are able to cleave the anhMurNAc-l -Ala bond. The activity was present only in the outer membrane fraction obtained from anampD mutant. In contrast to AmpD, which is specific for the anhMurNAc-l -alanine bond, AmiD also cleaved the bond between MurNAc andl -alanine in both muropeptides and murein sacculi. Unlike the periplasmic murein amidases, AmiD did not participate in cell separation.ampG mutants, which are unable to import GlcNAc-anhMurNAc-peptides into the cytoplasm, released mainly peptides into the medium due to AmiD activity, whereas anampG amiD double mutant released a large amount of intact GlcNAc-anhMurNAc-peptides into the medium.