Fungal GH25 muramidases: New family members with applications in animal nutrition and a crystal structure at 0.78Å resolution

Abstract

Muramidases/lysozymes hydrolyse the peptidoglycan component of the bacterial cell wall. They are found in many of the glycoside hydrolase (GH) families. Family GH25 contains muramidases/lysozymes, known as CH type lysozymes, as they were initially discovered in the Chalaropsis species of fungus. The characterized enzymes from GH25 exhibit both β-1,4-N-acetyl- and β-1,4-N,6-O-diacetylmuramidase activities, cleaving the β-1,4-glycosidic bond between N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) moieties in the carbohydrate backbone of bacterial peptidoglycan. Here, a set of fungal GH25 muramidases were identified from a sequence search, cloned and expressed and screened for their ability to digest bacterial peptidoglycan, to be used in a commercial application in chicken feed. The screen identified the enzyme from Acremonium alcalophilum JCM 736 as a suitable candidate for this purpose and its relevant biochemical and biophysical and properties are described. We report the crystal structure of the A. alcalophilum enzyme at atomic, 0.78 Å resolution, together with that of its homologue from Trichobolus zukalii at 1.4 Å, and compare these with the structures of homologues. GH25 enzymes offer a new solution in animal feed applications such as for processing bacterial debris in the animal gut.

Module walking using an SH3-like cell-wall-binding domain leads to a new GH184 family of muramidases

“…3.1. A fungal GH24 muramidase with a CWBD from T. saccata A broad bioinformatic screening for new muramidases from known GH families (GH22-GH25; Taylor et al, 2019;Moroz et al, 2021) led to the discovery of an enzyme from T. saccata with an extra domain attached to the catalytic GH24 domain. As described below, we demonstrate that this is an SH3-like cell-wall-binding domain (CWBD).…”

“…Screening for new enzymes with muramidase activity with potential benefits for industrial application in poultry feeds, where the enzymes can degrade bacterial cell-wall residues, previously led to the identification of the first commercial product, a GH25 enzyme from Sodiomyces alcalophilus marketed as Balancius TM (Moroz et al, 2021;. The screening project not only included GH25 muramidases but also other muramidase families known to be present in fungal taxa at the time: GH23 and GH24.…”

Tandem mass tag-based quantitative proteomics analyses of a chicken-original virulent and its attenuated Histomonas meleagridis strain in China

“…It was finally noticed that GH family 25 lysozyme presented the highest up-regulation in virulence strain. Lysozyme is a hydrolase of bacterial cell wall peptidoglycan (39). And an important feature of H. meleagridis is its complex interaction with bacteria, both in vivo and in vitro (40).…”