Pseudopeptidoglycan is a major cell wall

Cell wall

The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

 component of some archaea

Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

 that differs from bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l peptidoglycan

Peptidoglycan

Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β- linked N-acetylglucosamine and N-acetylmuramic acid...

 in chemical structure, but resembles eubacterial peptidoglycan in morphology, function, and physical structure. The basic components are N-acetylglucosamine

N-Acetylglucosamine

N-Acetylglucosamine is a monosaccharide derivative of glucose. It is an amide between glucosamine and acetic acid...

 and N-acetyltalosaminuronic acid

N-Acetyltalosaminuronic acid

N-Acetyltalosaminuronic acid is a uronic acid. It is a component of pseudopeptidoglycan, a structural polymer found in the cell walls in some types of Archaea....

 (peptidoglycan has N-acetylmuramic acid

N-Acetylmuramic acid

N-Acetylmuramic acid, or MurNAc, is the ether of lactic acid and N-acetylglucosamine with a chemical formula of C11H19NO8. It is part of a biopolymer in the bacterial cell wall, built from alternating units of N-acetylglucosamine and N-acetylmuramic acid , cross-linked with oligopeptides at the...

 instead), which are linked by β-1,3-glycosidic bonds. Lysozyme

Lysozyme

Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, are glycoside hydrolases, enzymes that damage bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between...

, a host defense mechanism, is ineffective against organisms with pseudopeptidoglycan cell walls. Lysozyme can break β-1,4-glycosidic bonds to degrade peptidoglycan; however, pseudopeptidoglycan has β-1,3-glycosidic bonds, rendering lysozyme useless.