Disclosed herein are compounds and methods for detecting enzyme activity. In some embodiments, the enzyme is a deacetylase enzyme such as HDAC. The compound of the invention comprises a detectable label, a linker, and an enamide group. The compound can be enzymatically cleaved by the enzyme of interest to produce a nucleophilic fragment that includes the detectable label. Measurement of a signal generated by the detectable label can indicate enzyme activity. The compounds can be used as either in vivo or in vitro enzyme probes.
