Editing Autolysin (section)

== Function and mechanisms ==
[[File:Peptidoglycan-membrane.png|thumb|331x331px|Peptidoglycan Cell Wall and their Cross Linked Peptides]]
Autolysins exist in all [[bacteria]] containing [[peptidoglycan]] and are potentially considered as lethal enzymes when uncontrolled.<ref>{{cite journal | vauthors = Haghighat S, Siadat SD, Sorkhabadi SM, Sepahi AA, Mahdavi M | title = Cloning, expression and purification of autolysin from methicillin-resistant Staphylococcus aureus: potency and challenge study in Balb/c mice | journal = Molecular Immunology | volume = 82 | pages = 10–18 | date = February 2017 | pmid = 28006655 | doi = 10.1016/j.molimm.2016.12.013 | s2cid = 36593600 }}</ref> They target the glycosidic bonds as well as the cross-linked peptides of the peptidoglycan matrix.<ref name="pmid24692449">{{cite journal | vauthors = Atilano ML, Pereira PM, Vaz F, Catalão MJ, Reed P, Grilo IR, Sobral RG, Ligoxygakis P, Pinho MG, Filipe SR | display-authors = 6 | title = Bacterial autolysins trim cell surface peptidoglycan to prevent detection by the Drosophila innate immune system | journal = eLife | volume = 3 | pages = e02277 | date = April 2014 | pmid = 24692449 | pmc = 3971415 | doi = 10.7554/eLife.02277 | doi-access = free }}</ref> The peptidoglycan matrix functions for cell wall stability to protect from turgor changes and carries out function for immunological defense.<ref>{{cite journal | vauthors = Zhang Y, Zhong X, Lu P, Zhu Y, Dong W, Roy S, Hejair HM, Pan Z, Ma J, Yao H | display-authors = 6 | title = A novel autolysin AtlA<sub>SS</sub> mediates bacterial cell separation during cell division and contributes to full virulence in Streptococcus suis | journal = Veterinary Microbiology | volume = 234 | pages = 92–100 | date = July 2019 | pmid = 31213278 | doi = 10.1016/j.vetmic.2019.05.020 | s2cid = 182382454 }}</ref><ref>{{cite book | vauthors = Pazos M, Peters K | title = Bacterial Cell Walls and Membranes | chapter = Peptidoglycan | series = Subcellular Biochemistry | volume = 92 | pages = 127–168 | date = 2019 | pmid = 31214986 | doi = 10.1007/978-3-030-18768-2_5  | publisher = Springer International Publishing | isbn = 978-3-030-18767-5 | s2cid = 239142525 | editor-first = Andreas | editor-last = Kuhn }}</ref> These enzymes break down the peptidoglycan matrix in small sections to allow for peptidoglycan biosynthesis.<ref name=":0" /> Autolysins breaks down old peptidoglycan which allows for the formation of newer peptidoglycan for cell growth and elongation. This is called cell wall turnover.<ref name=":1" /> Autolysins do this by hydrolyzing the β-(1,4) glycosidic bond of the peptidoglycan cell wall and the linkage between N-acetylmuramoyl residues and L-amino acid residues of certain cell-wall glycopeptides.<ref name=":0" /> This enzyme [[catalysis|catalyses]] the following [[chemical reaction]]:

: Cleavage of the [[proline]]- and [[hydroxyproline]]-rich proteins of the ''[[Chlamydomonas]]'' [[cell wall]]; also cleaves [[azocasein]], [[gelatin]] and Leu-Trp-Met-Arg-Phe-Ala

This glycoprotein is present in ''[[Chlamydomonas reinhardtii]]'' [[gamete]]s.

[[Gram-positive]] bacteria regulate autolysins with [[teichoic acid]] molecules attached to the tetrapeptide of the peptidoglycan matrix.

The [[antibiotic]]s complestatin and [[corbomycin]] prevent autolysin from remodeling the cell wall by binding to peptidoglycan, therefore stopping bacterial growth.<ref name="CulpWaglechner2020">{{cite journal | vauthors = Culp EJ, Waglechner N, Wang W, Fiebig-Comyn AA, Hsu YP, Koteva K, Sychantha D, Coombes BK, Van Nieuwenhze MS, Brun YV, Wright GD | display-authors = 6 | title = Evolution-guided discovery of antibiotics that inhibit peptidoglycan remodelling | journal = Nature | volume = 578 | issue = 7796 | pages = 582–587 | date = February 2020 | pmid = 32051588 | doi = 10.1038/s41586-020-1990-9 | s2cid = 211089119 | bibcode = 2020Natur.578..582C }}</ref> The amide linkages between stem peptide and lactyl moiety of muramoyl residue are cleaved by [[N-acetylmuramoyl-L-alanine amidase|N-acetylmuramoyl-l-alanine amidases]] and partakes in cell separation and the dissociation of the cell septum.<ref name=":0" /> There are 5 types of autolysins that contribute to cell separation of daughter cells, LytC, LytD, LytE, and LytF.<ref name=":1" />

In a study conducted with mice, those that were immunized with autolysin were able to survive longer than the infected mice. This study was able to support as evidence autolysin's contribution in virulence and potential for vaccine antigen.<ref name=":3">{{cite journal | vauthors = Berry AM, Lock RA, Hansman D, Paton JC | title = Contribution of autolysin to virulence of Streptococcus pneumoniae | journal = Infection and Immunity | volume = 57 | issue = 8 | pages = 2324–2330 | date = August 1989 | pmid = 2568343 | pmc = 313450 | doi = 10.1128/iai.57.8.2324-2330.1989 | doi-access = free }}</ref>

=== Lysis of mother cell ===
{{Infobox enzyme|name=N-acetylmuramoyl-L-alanine amidase|EC_number=3.5.1.28|CAS_number=9013-25-6|GO_code=GO:0008745}}
LytC and CwlC are two [[amidase]]s from the LytC family that hydrolyze the peptidoglycan of the mother cell wall to allow for the release of the mature endospore. CwlC is directly found in the mother cell wall.<ref name=":1" />

=== Motility ===
Expression of lytC, lytD, and lytF genes together leads to flagellar motility and is controlled by the activity of the chemotaxis sigma factor,  σ<sup>D</sup>. The activity of this sigma factor peaks at the start of the stationary phase.<ref name=":1" />

=== Potential lethality ===
Autolysins are naturally produced by peptidoglycan containing bacteria, but excessive amounts will degrade the peptidoglycan matrix and cause the cell to burst due to [[osmotic pressure]]. Previous studies have found that the byproducts of autolysin during cell wall breakdown are highly immunogenic.<ref name=":3" /> When observed in the bacteria, ''[[Bacillus subtilis]]'', there were potentially lethal amounts of autolysin found in the cell walls.<ref name=":1" /> In ''Streptococcus pneumoniae'' it was found that N-acetylmuramoyl-l-alanine amidase, a cell wall autolysin, could assist in pathogenesis due to its ability to break down the wall or lyse a portion of the invading pneumococci and release potentially lethal toxins into the cell. Researchers studied the function, structure, and cloning ability through ''Escherichia coli'' and also determined its nucleotide sequence.<ref name=":3" />