Endo-N-acetylmuramidases (muramidases) are lysozymes (also referred to as peptidoglycan hydrolases) that degrade bacterial cell walls by catalyzing the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues. This family of muramidases contains a glycosyl hydrolase family 25 (GH25) catalytic domain and is found in bacteria, fungi, slime molds, round worms, protozoans and bacteriophages. The bacteriophage members are referred to as endolysins which are involved in lysing the host cell at the end of the replication cycle to allow release of mature phage particles. Endolysins are typically modular enzymes consisting of a catalytically active domain that hydrolyzes the peptidoglycan cell wall and a cell wall-binding domain that anchors the protein to the cell wall. Endolysins generally have narrow substrate specificities with either intra-species or intra-genus bacteriolytic activity.

YegX is an uncharacterized bacterial protein with a glycosyl hydrolase family 25 (GH25) catalytic domain that is similar in sequence to the CH-type (Chalaropsis-type) lysozymes of the GH25 family of endolysins.

CH-type (Chalaropsis-type) lysozymes represent one of four functionally-defined classes of peptidoglycan hydrolases (also referred to as endo-N-acetylmuramidases) that cleave bacterial cell wall peptidoglycans. CH-type lysozymes exhibit both lysozyme (acetylmuramidase) and diacetylmuramidase activity. The first member of this family to be described was a muramidase from the fungus Chalaropsis. However, a majority of the CH-type lysozymes are found in bacteriophages and Gram-positive bacteria such as Streptomyces and Clostridium. CH-type lysozymes have a single glycosyl hydrolase family 25 (GH25) domain with an unusual beta/alpha-barrel fold in which the last strand of the barrel is antiparallel to strands beta7 and beta1. Most CH-type lysozymes appear to lack the cell wall-binding domain found in other GH25 muramidases.

Glycosyl hydrolases family 25.

Lyc muramidase is an autolytic lysozyme (autolysin) from Clostridium acetobutylicum encoded by the lyc gene. Lyc has a glycosyl hydrolase family 25 (GH25) catalytic domain. Endo-N-acetylmuramidases are lysozymes (also referred to as peptidoglycan hydrolases) that degrade bacterial cell walls by catalyzing the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues.

Crystalstructure of the bacterial lysozyme from Streptomyces coelicolor at 1.65 A resolution [Streptomyces coelicolor]

Thestructure of a family GH25 lysozyme from Aspergillus fumigatus [Aspergillus fumigatus Af293],2X8R_B The structure of a family GH25 lysozyme from Aspergillus fumigatus [Aspergillus fumigatus Af293],2X8R_C The structure of a family GH25 lysozyme from Aspergillus fumigatus [Aspergillus fumigatus Af293],2X8R_D The structure of a family GH25 lysozyme from Aspergillus fumigatus [Aspergillus fumigatus Af293],2X8R_E The structure of a family GH25 lysozyme from Aspergillus fumigatus [Aspergillus fumigatus Af293],2X8R_F The structure of a family GH25 lysozyme from Aspergillus fumigatus [Aspergillus fumigatus Af293]

ChainA, muramidase [Trichobolus zukalii],6ZMV_B Chain B, muramidase [Trichobolus zukalii]

X-raystructure of catalytic domain of endolysin from clostridium perfringens phage phiSM101 [Clostridium phage phiSM101]

ChainA, muramidase [Sodiomyces alcalophilus]

Uncharacterized protein YegX OS=Escherichia coli O157:H7 OX=83334 GN=yegX PE=3 SV=2

Uncharacterized protein YegX OS=Escherichia coli (strain K12) OX=83333 GN=yegX PE=3 SV=2

Uncharacterized protein YegX OS=Escherichia coli O6:H1 (strain CFT073 / ATCC 700928 / UPEC) OX=199310 GN=yegX PE=3 SV=2

Lysozyme M1 OS=Streptomyces globisporus OX=1908 GN=acm PE=1 SV=1

N,O-diacetylmuramidase OS=Chalaropsis sp. OX=36534 PE=1 SV=1