Provided herein and methods and kits for identifying inhibitors of SUMOylation. The provided methods include contacting a candidate agent with (i) a SUMO-conjugating peptide comprising an N-terminal linker and a detectable tag, and (ii) a SUMO comprising a metal complex, under conditions that allow binding between the SUMO-conjugating peptide and the SUMO, and detecting the detectable tag thereby determining the level of binding between the SUMO-conjugating peptide and SUMO. A reduced level of binding as compared to the level of binding in the absence of the candidate agent indicating the agent inhibits SUMOylation.