Glycoside Hydrolase Family 25

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• Author: ^^^Ed Taylor^^^
• Responsible Curator: ^^^Gideon Davies^^^

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Glycoside Hydrolase Family GHnn
Clan	GH-x
Mechanism	retaining/inverting
Active site residues	known/not known
CAZy DB link
http://www.cazy.org/fam/GHnn.html

Substrate specificities

Substrate specificities Family GH25 lysozymes otherwise known as Chalaropsis (CH) type of lysozymes (from is initial characterisation from Chalaropsis species of fungus[1]) cleaves the β-1,4-glycosidic bond between N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) in the carbohydrate backbone of bacterial peptidoglycan. The characterized lysozymes from this family exhibit both β-1,4-N-acetyl- and β-1,4- N ,6-O-diacetylmuramidase activities and are able to degrade O-acetylated peptidoglycan present in Staphylococcus aureus and other pathogens2. The activity of GH25 enzymes appears to fulfil two main biological roles in bacteria. These roles are the re-modelling of peptidoglycan in cellular process such as division and promoting the dissemination of phage progeny toward the end of the phage lytic cycle, which is achieved by bacterial cell lysis. For this reason many GH25 proteins are found to be either chromosomal, phage or prophage encoded. The majority of the GH25 family is comprised of bacterial or prokaryotic viral (phage) members. There are however a few eukaryotic representatives, but these are so far restricted to the fungal kingdom. The roles of these fungal enzymes are less clear, many possess signal secretion peptides indicating a likely extracellular location, possibly for the purpose of obtaining or gaining assess to nutrients or even as a selective agent against bacteria.

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

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Family Firsts

First sterochemistry determination

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First catalytic nucleophile identification

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First general acid/base residue identification

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First 3-D structure

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References

1. Hash JH, Rothlauf MV. The N,O-diacetylmuramidase of Chalaropsis species. I. Purification and crystallization. J Biol Chem 1967;242(23):5586-5590.