Functional proteomic profiling of glycan-processing enzymes

Glycoconjugates play critical roles in regulating cellular and organismal functions. Consequently, defining the relative levels of these glycoconjugates under varied physiological conditions is important. Thus identifying and understanding the regulation of the enzymes that process these glycoconjugates are essential steps in understanding the role of this "glycocode" in development and disease. Activity-based affinity reagents are useful tools for probing these enzymes and should facilitate the unraveling of proteomes. One advantage of activity-based affinity probes is that they can simultaneously reveal multiple enzymes having similar activities. These probes can also be used to enrich proteomes of interest, thereby facilitating identification and cloning of new carbohydrate-processing enzymes. Here we review the current state of activity-based affinity probes for profiling carbohydrate-processing enzymes, focusing on successes and limitations, general design features, and a specific example describing profiling of exoglycosidases from cell lysates.