Cy5-Ub-VME is a potent, irreversible and specific inhibitor of deubiquitinating enzymes (DUBs), which is labeled on the N-terminus with a Cy5 dye (Cy5, Ex 625-650 nm, Em 670 nm). This ubiquitin-based activity probe can be used for activity profiling experiments and labeling of DUBs with a fluorescent dye (Cy5). Cy5 labelling allows for detection of DUB labeling by in-gel fluorescence.?