Pseudopeptidoglycan

Structure schematic, showing sugar units and UDP-L-Glu-γ-L-Ala-ε-L-Lys-L-Ala peptide stem. Additional glutamic acid residue attached to the L-Lys residue via a γ bond[1] not shown.

Pseudopeptidoglycan (also known as pseudomurein;[2] PPG hereafter) 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.[3]

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. It was thought from these large differences in cell wall chemistry that archaeal cell walls and bacterial cell walls have not evolved from a common ancestor but are only the result of a convergent evolution,[4] but recent structural work has revealed deeper homology.[1]

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.[5] The pseudomurein endoisopeptidases function by cleaving the peptide links between adjacent pseudopeptidoglycan strands.

  1. ^ a b Cite error: The named reference syn was invoked but never defined (see the help page).
  2. ^ White, David. (1995) The Physiology and Biochemistry of Prokaryotes, pages 6, 12-21. (Oxford: Oxford University Press). ISBN 0-19-508439-X.
  3. ^ 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 1 November 2024), PMID 28876866, retrieved 2021-04-19{{citation}}: CS1 maint: DOI inactive as of November 2024 (link)
  4. ^ 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.
  5. ^ 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.