The complex, dynamic nature of ubiquitylation demands a suite of cutting-edge assays to measure the activity of ubiquitin (Ub) system enzymes. Removal of polyubiquitin chains from substrate proteins alters the fate of those substrates, rescuing substrates from proteasomal degradation or preventing another ubiquitin-dependent cellular event such as protein trafficking, mitophagy, autophagy or initiation of a stress response pathway. LifeSensors has developed number assays for measuring DUB activity. These assays rely on innovative yet simple ubiquitin-based fluorescent probes for recapitulating the native activity of DUBs.