Activity‐Based Protein Profiling of Chitin Catabolism

The microbial catabolism of chitin, an abundant and ubiquitous environmental organic polymer, is a fundamental cog in terrestrial and aquatic carbon and nitrogen cycles. Despite the importance of this critical bio‐geochemical function, there is a limited understanding of the synergy between the various hydrolytic and accessory enzymes involved in chitin catabolism. To address this deficit, we synthesized activity‐based probes (ABPs) designed to target active chitinolytic enzymes by modifying the chitin subunits N‐acetyl glucosamine and chitotriose. The ABPs were used to determine the active complement of chitinolytic enzymes produced over time by the soil bacterium Cellvibrio japonicus treated with various C substrates. We demonstrate the utility of these ABPs in determining the synergy between various enzymes involved in chitin catabolism. The strategy can be used to gain molecular‐level insights that can be used to better understand microbial roles in soil bio‐geochemical cycling in the face of a changing climate. Trying to fit in chitin: To understand microbial chitinase function, we synthesized activity‐based probes by modifying the chitin derivatives chitotriose and N‐acetylglucosamine. The probes were used to profile the functional response of Cellvibrio japonicus to culture on chitin and non‐chitin substrates. Fluorescence gels and proteomics were used to characterize probe labeling.