Pseudopeptidoglycan

Pseudopeptidoglycan (also known as pseudomurein[1]) is a major cell wall component of some Archaea that differs from bacterial peptidoglycan in chemical structure, but resembles bacterial peptidoglycan in function and physical structure. Pseudopeptidoglycan, in general, is only present in a few methanogenic archaea. The basic components are N-acetylglucosamine and N-acetyltalosaminuronic acid (bacterial peptidoglycan containing N-acetylmuramic acid instead), which are linked by β-1,3-glycosidic bonds.[2]

Lysozyme, a host defense mechanism present in human secretions (e.g. saliva and tears) breaks β-1,4-glycosidic bonds to degrade peptidoglycan. However, because pseudopeptidoglycan has β-1,3-glycosidic bonds, lysozyme is ineffective. These fundamental differences in cell wall chemistry suggest that archaeal cell walls and bacterial cell walls have not evolved from a common ancestor but are only the result of a convergent evolution.[3]

No archaeal enzymes are known that cleave the β-1,3-glycosidic bonds in pseudopeptidoglycan, but it can be degraded by pseudomurein endoisopeptidase encoded by two prophages.[4] The pseudomurein endoisopeptidases function by cleaving the peptide links between adjacent pseudopeptidoglycan strands.

Structure

Pseudopeptidoglycan is composed of two sugars, N-acetylglucosamine and N-acetyltalosaminuronic acid. These sugars are made of different amino acids, and the peptide cross-links within pseudopeptidoglycan are formed with different amino acids. The peptide bond is formed between the lysine of a N-acetyltalosaminuronic acid and a glutamine of a parallel N-acetyltalosaminuronic acid.[5] Pseudopeptidoglycan, like peptidoglycan in bacteria, forms a mesh-like layer outside of the plasma membrane of the archaea.

Function

Only a few methanogenic archaea have cell walls composed of pseudopeptidoglycan. This component functions much like peptidoglycan in a bacterial cell.[6] Pseudopeptidoglycan is used by the archaeal cell to determine its shape and provide structure to the cell. It is also used to protect the cell from undesired molecules or anything harmful in its environment.

Effects of different bacterial medicines on pseudopeptidoglycan

Lysozyme

Lysozyme is a natural defense mechanism in humans that has the ability to break down peptidoglycan in bacterial cells. It degrades the peptidoglycan by targeting the β-1,4-glycosidic bonds that connect the alternating amino sugars in which it is composed of.[7] This degradation of the glycosidic bonds within peptidoglycan cause the sugars to separate and inhibit the structural integrity of the peptidoglycan and the bacteria.

Pseudopeptidoglycan, however, is composed of a different acidic amino sugar, which is N-acetyltalosaminuronic acid. This difference is the reason that it has β-1,3-glycosidic bonds (as opposed to the β-1,4-glycosidic bonds in bacteria).[2] Lysozymes targets the linkage in peptidoglycan, and without that, becomes ineffective against pseudopeptidoglycan.

Penicillin

Penicillin is a group of antibiotics that have been effective against many bacterial infections. It attacks bacteria by targeting and inhibiting the transpeptidase that catalyzes the cross-linking of the amino sugars in peptidoglycan.[8] However, peptidoglycan contains different amino sugars, and therefore, a different catalysis enzyme is used. The different amino acids cause antibiotics, that target cell walls like penicillin, to be ineffective against pseudopeptidoglycan.[5]

Examples of archaeal genus

See also

References

  1. ↑ White, David. (1995) The Physiology and Biochemistry of Prokaryotes, pages 6, 12-21. (Oxford: Oxford University Press). ISBN 0-19-508439-X.
  2. 1 2 Albers, Sonja; Eichler, Jerry; Aebi, Markus (2015), Varki, Ajit; Cummings, Richard D.; Esko, Jeffrey D.; Stanley, Pamela (eds.), "Archaea", Essentials of Glycobiology (3rd ed.), Cold Spring Harbor (NY): Cold Spring Harbor Laboratory Press, doi:10.1101/glycobiology.3e.022 (inactive 31 October 2021), PMID 28876866, retrieved 2021-04-19{{citation}}: CS1 maint: DOI inactive as of October 2021 (link)
  3. ↑ Visweswaran, Ganesh Ram R.; Dijkstra, Bauke W.; Kok, Jan (2011). "Murein and pseudomurein cell wall binding domains of bacteria and archaea—a comparative view". Applied Microbiology and Biotechnology. 92 (5): 921–928. doi:10.1007/s00253-011-3637-0. ISSN 0175-7598. PMC 3210951. PMID 22012341.
  4. ↑ Visweswaran, Ganesh Ram R.; Dijkstra, Bauke W.; Kok, Jan (2010). "Two Major Archaeal Pseudomurein Endoisopeptidases: PeiW and PeiP". Archaea. 2010: 480492. doi:10.1155/2010/480492. PMC 2989375. PMID 21113291.
  5. 1 2 Slonczewski, Joan, Watkins, John, Foster.; Slonczewski, Joan (2009). Microbiology: An Evolving Science.{{cite book}}: CS1 maint: multiple names: authors list (link)
  6. ↑ "Peptidoglycan vs Pseudopeptidoglycan | Easy Biology Class". www.easybiologyclass.com. 2017-05-19. Retrieved 2021-05-06.
  7. ↑ Primo, Emiliano D.; Otero, Lisandro H.; Ruiz, Francisco; Klinke, Sebastián; Giordano, Walter (2018). "The disruptive effect of lysozyme on the bacterial cell wall explored by an in-silico structural outlook". Biochemistry and Molecular Biology Education. 46 (1): 83–90. doi:10.1002/bmb.21092. ISSN 1539-3429. PMID 29131507.
  8. ↑ Yocum, R. R.; Rasmussen, J. R.; Strominger, J. L. (1980-05-10). "The mechanism of action of penicillin. Penicillin acylates the active site of Bacillus stearothermophilus D-alanine carboxypeptidase". The Journal of Biological Chemistry. 255 (9): 3977–3986. doi:10.1016/S0021-9258(19)85621-1. ISSN 0021-9258. PMID 7372662.

Further reading

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