Glycoside Hydrolase Family 73

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• Author: ^^^Florence Vincent^^^
• Responsible Curator: ^^^Bernard Henrissat^^^

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Glycoside Hydrolase Family GH73
Clan	none, α+β "lysozyme fold"
Mechanism	not known
Active site residues	partially known
CAZy DB link
https://www.cazy.org/GH73.html

Substrate specificities

         Normal.dotm  0  0  1  177  1010  CNRS  8  2  1240  12.0         0  false    21    18 pt  18 pt  0  0    false  false  false

The GH73 family is comprised of bacterial or prokaryotic viral members. Most of the enzymes of this family are peptidoglycan hydrolases that cleave the β-1,4-glycosidic linkage between N-acetylglucosaminyl (NAG) and N-acetylmuramyl (NAM) moieties in the carbohydrate backbone of bacterial peptidoglycan.

The activity of the GH73 is mainly focused in daughter cell separation during vegetative growth and it is very often involved in the hydrolysis of the septum after cell division (Acp from C. Perf (20190047) AltA from E. faecalis(17041059). Only Listeria monocytogene uses Auto as a virulence associated peptidoglycan hydrolase for host-cell invasion (ref). The GH73 are mostly surface located and exhibit repeated sequences that could be involved in cell-wall binding and therefore reinforce the enzymes catalytic activity. Unknown repeated domains are appended for instance to LytC LytD and LytG from Bacillus subtilis (ref/ref/ref), AcmB from Lactococcus lactis (ref) and Auto from L. monocytogene. Some of these repeated domains have been identified like CBM50 also known as LysM domain appended to AcmA for Lactococcsu lactis (ref), AltA from Enterococcus faecalis (ref) and Mur2-Mur2 from Enterococcus hirae(ref).

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

Figure 1. Ribbon diagram of Auto structure (orange) and its surface, superimposed on FlgJ structure (green).

Crystal structure of GH73 are available and have been coincidently reported, FlgJ from Sphingomonas sp. (SPH1045-C) [1] and Auto a virulence associated peptigoglycan hydrolase from Listeria monocytogenes [2]. A structure for a catalytic mutant (E185A) of FlgJ has been solved by Maruyama et al [3] but doesn’t show any conformational changes. The two GH73 show the same fold, with two subdomains consisting of a β-lobe and an α-lobe that together create an extended substrate binding groove (Figure 1). With a typical lysozyme (α+β) fold, the catalytic domain of Auto is structurally related to the catalytic domain of Slt70 from E. coli [4], the family GH19 chitinases and goose egg-white lysozyme (GEWL, GH23)[5]. FlgJ is structurally related to a peptidoglycan degrading enzyme from the bacteriophage phi 29 [6] and also to family GH22 and GH23 lysozymes.

Family Firsts

First stereochemistry 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

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