Murein vs Pseudomurein
The majority of Bacteria and Archaebacteria have a rigid cell wall around its plasma membrane. The peptidoglycan (also called murein) cell wall, which is considered as the biomarker of bacteria, is absent in the cell wall of Archaea. However, the members of Archaea show great diversity in their cell wall composition. The cell wall in Archaea may contain polysaccharides, proteins or glycoproteins. Some methanogenic Archaebacteria possess a cell wall molecule that is remarkably similar to that of the peptidoglycan molecules in the cell wall of bacteria.
These cell wall molecules are called Pseudopeptidoglycan or Pseudomurein. The peptidoglycan and pseudopeptidoglycan shows many structural and functional similarities and differences. The present post describes the Similarities and Differences between the Peptidoglycan (Murein) and Pseudopeptidoglycan (Pseudomurein) with a comparison table.
Similarities between Peptidoglycan (Murein) and Pseudopeptidoglycan (Pseudomurein)
Ø. Both Peptidoglycan and Pseudopeptidoglycan are glycoconjugates.
Ø. Both are polymers of monomer units joined by specific glycosidic bonds.
Ø. Both are hetero-polysaccharides (consists of more than one type of monomer units).
Ø. Both contain long un-branched carbohydrate chains inter-connected by short peptide segments.
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Ø. Both murein and pseudomurein have same function in the cell, i.e., provide protection.
Ø. The building blocks (monomer units) of the cell wall are linked by β-glycosidic bonds.
Ø. Both murein and pseudomurein contain N-Acetylglucosamine residues.
Ø. Both form mesh like layer outside the plasma membrane of the cell.
Ø. Both have more or less similar morphology and physical properties.
Difference between Peptidoglycan (Murein) and Pseudopeptidoglycan (Pseudomurein)
Sl. No. Peptidoglycan Pseudopeptidoglycan 1 Commonly called as Murein. Commonly called as Pseudomurein. 2 Found in the cell wall of Bacteria. Found in the cell wall of Archaebacteria. 3 Carbohydrate building blocks are N-acetylglucosamie (NAG) and N-acetylmuramicacid (NAM). Carbohydrate building blocks are N-acetylglucosamine (NAG) and N-acetyltalosaminuronicacid (NAT). 4 Individual carbohydrate units are connected by β 1 – 4 glycosidic linkages. Individual carbohydrate units are connected by β 1 – 3 glycosidic linkages. 5 The peptide cross links contain both D and L amino acids. The peptide cross links contain only L amino acids. 6 The amino acid sequence of peptide cross link is L – Alanine, D - Glutamine, L – Lysine and D – Alanine* The amino acid sequence of peptide cross link is L - Glutamine, L – alanine, L – Lysine and L – Glutamine* 7 The cell wall may contain Diaminopimelic acid (DAP), a structural analog and derivative of Lysine Diaminopimelic acid is completely absent and it is not reported in the cell wall of any Archaebacteria 8 Antibiotics such as Vancomycin and Penicillin can degrade the peptidoglycan cell wall. Vancomycin and Penicillin are insensitive to pseudopeptidoglycan and they cannot degrade it. 9 Peptidoglycan is sensitive to the activity of Lysozyme enzyme. Pseudopeptidoglycan is insensitive to the activity of Lysozyme enzyme.
* Different groups may show variation. This sequence is the most common one.