N-acetylmuramoyl-L-alanine amidase or MurNAc-LAA (also known as peptidoglycan aminohydrolase, NAMLA amidase, NAMLAA, Amidase 3, and peptidoglycan amidase; EC 3.5.1.28) is an autolysin that hydrolyzes the amide bond between N-acetylmuramoyl and L-amino acids in certain cell wall glycopeptides. These proteins are Zn-dependent peptidases with highly conserved residues involved in cation co-ordination. MurNAc-LAA in this family is one of several peptidoglycan hydrolases (PGHs) found in bacterial and bacteriophage or prophage genomes that are involved in the degradation of the peptidoglycan. In Escherichia coli, there are five MurNAc-LAAs present: AmiA, AmiB, AmiC and AmiD that are periplasmic, and AmpD that is cytoplasmic. Three of these (AmiA, AmiB and AmiC) belong to this family, the other two (AmiD and AmpD) do not. E. coli AmiA, AmiB and AmiC play an important role in cleaving the septum to release daughter cells after cell division. In general, bacterial MurNAc-LAAs are members of the bacterial autolytic system and carry a signal peptide in their N-termini that allows their transport across the cytoplasmic membrane. However, the bacteriophage MurNAc-LAAs are endolysins since these phage-encoded enzymes break down bacterial peptidoglycan at the terminal stage of the phage reproduction cycle. As opposed to autolysins, almost all endolysins have no signal peptides and their translocation through the cytoplasmic membrane is thought to proceed with the help of phage-encoded holin proteins. The amidase catalytic module is fused to another functional module (cell wall binding module or CWBM) either at the N- or C-terminus, which is responsible for high affinity binding of the protein to the cell wall.

N-acetylmuramoyl-L-alanine amidase [Cell wall/membrane/envelope biogenesis].

N-acetylmuramoyl-L-alanine amidase. This enzyme domain cleaves the amide bond between N-acetylmuramoyl and L-amino acids in bacterial cell walls.

N-acetylmuramoyl-L-alanine amidase CwlD. Members of this protein family are the CwlD family of N-acetylmuramoyl-L-alanine amidase. This family has been called the germination-specific N-acetylmuramoyl-L-alanine amidase. CwlD is required, along with the putative deactylase PdaA, to make muramic delta-lactam, a novel peptidoglycan constituent found only in spores. CwlD mutants show a germination defect. [Cell envelope, Biosynthesis and degradation of murein sacculus and peptidoglycan, Cellular processes, Sporulation and germination]

Ami_3 domain.

Structureof the catalytic domain of CwlV, N-acetylmuramoyl-L-alanine amidase from Bacillus(Paenibacillus) polymyxa var.colistinus [Paenibacillus polymyxa]

ChainA, N-acetylmuramoyl-L-alanine amidase [Clostridioides difficile 630]

ChainA, Cell wall hydrolase/autolysin [Nostoc punctiforme PCC 73102]

ChainB, Germination-specific N-acetylmuramoyl-L-alanine amidase, Autolysin [Clostridioides difficile]

Crystalstructure of the E. coli N-acetylmuramoyl-L-alanine amidase AmiC [Escherichia coli K-12]

Uncharacterized protein YqiI OS=Bacillus subtilis (strain 168) OX=224308 GN=yqiI PE=3 SV=3

N-acetylmuramoyl-L-alanine amidase LytC OS=Bacillus subtilis (strain 168) OX=224308 GN=lytC PE=1 SV=1

Sporulation-specific N-acetylmuramoyl-L-alanine amidase OS=Bacillus subtilis (strain 168) OX=224308 GN=cwlC PE=1 SV=1

Probable cell wall amidase LytH OS=Staphylococcus epidermidis (strain ATCC 12228 / FDA PCI 1200) OX=176280 GN=lytH PE=3 SV=1

Probable cell wall amidase LytH OS=Staphylococcus epidermidis (strain ATCC 35984 / RP62A) OX=176279 GN=lytH PE=3 SV=1