De-N-acetylation of cell wall chitin/pepitdoglycan as a defence mechanism against the mammalian immune system - structures, mechanisma and inhibitor development. (360G-Wellcome-078472_B_05_A)

One of the primary defences of the innate mammalian immune system against microbial pathogens is secretion of cell wall-targeted lytic glycoside hydrolases. Some of these enzymes, lysozymes (degrading peptidoglycan) and chitinases (degrading chitin), heavily depend on the presence of the N-acetyl side chains on N-acetylglucosamine for substrate recognition. Recent research has suggested that bacteria, fungi and microsporidia possess carbohydrate esterases ("family 4 carbohydrate esterases", CE-4) that partially de-N-acetylate cell wall peptidoglycan and chitin, thereby conferring microbial resistance against these mammalian glycoside hydrolases. Bacterial knockout studies of CE-4 esterases have shown that deletion of these genes results in hypersensitivity to lysozyme and dramatic reduction in virulence in a mouse model. This proposal aims to study the structure and molecular mechanism of action of microbial CE-4 esterases, screen small molecule libraries for inhibitors and synthesize potential leads using a combination of the resulting hits and rational design. These leads will then be tested in bacterial, fungal and microsporidian cultures in terms of resistance against lysozymes/chitinases and ultimately evaluated (through collaborations) in appropriate mouse models. Specifically, we will study the peptidoglycan deacetylases of the Streptococcus pneumoniae and the oral pathogen Streptococcus mutans, fungal chitin deacetylases from the pathogen Aspergillus fumigatus and the microsporidian chitin deacetylase from the pathogen Encephalitozoon cuniculi.