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

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

Ami_3 domain.

N-acetylmuramoyl-L-alanine amidase AmiA.

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

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

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

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

Thecrystal structure of a domain from N-acetylmuramoyl-l-alanine amidase of Bartonella henselae str. Houston-1 [Bartonella henselae]

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

N-acetylmuramoyl-L-alanine amidase AmiA OS=Escherichia coli (strain K12) OX=83333 GN=amiA PE=1 SV=1

N-acetylmuramoyl-L-alanine amidase AmiA OS=Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720) OX=99287 GN=amiA PE=3 SV=1

Probable cell wall amidase LytH OS=Staphylococcus saprophyticus subsp. saprophyticus (strain ATCC 15305 / DSM 20229 / NCIMB 8711 / NCTC 7292 / S-41) OX=342451 GN=lytH PE=3 SV=1