Cysteine proteases are attractive drug targets due to their involvement in a wide variety of diseases. To evaluate the potential of a particular protease as a drug target, use of a reagent that controls activity of the protease is indispensable. In this context, we have developed a catch-and-release reagent that first forms a covalent bond with the active center thiol of a cysteine protease to suppress its activity and then is removed by UV-irradiation to release ...