Activity-Based Protein Profiling Identifies an α-Amylase Family Protein Contributing to the Virulence of Methicillin-Resistant <i>Staphylococcus aureus</i>

In search of new putative antimicrobial drug targets in methicillin-resistant <i>Staphylococcus aureus</i>, we aimed to identify and characterize retaining glycosidase activities in this bacterial pathogen. Using activity-based protein profiling (ABPP), a panel of 7 fluorescent probes was screened to detect activities of diverse retaining glycosidase families. Based on this, a cocktail of 3 biotinylated probes (targeting α-glucosidases, β-galactosidases and α-fucosidases) was used for target enrichment and three glycoside hydrolase family proteins were identified by mass-spectrometry: 6-phospho-β-glucosidase (BglA), α-amylase family protein trehalase C (TreC), and autolysin (Atl). The physiological relevance of previously uncharacterized BglA and TreC was addressed in CRISPRi and inhibitor studies with the putative TreC inhibitor α-cyclophellitol-aziridine. Silencing of <i>tre</i>C did not affect bacterial growth in rich media, but reduced biofilm formation <i>in vitro</i>, and attenuated virulence during <i>Galleria mellonella</i> infection, warranting future investigations into the biochemical function of this enzyme.