The E2 Screening Kit II (Cat# J1300) contains ubiquitin (Ub)-activating enzyme (UbE1), SUMO-activating enzyme (6xHis-SAE1/SAE2), Nedd8-activating enzyme (APPBP1/6xHis-UBA3), Ub, SUMO2, Nedd8, and 29 Ub-conjugating enzymes (E2s). It can be used for 1) identification of the E2 enzyme paired for a specific Ub ligase (E3) for a protein substrate, and 2) assessing/profiling E2 activity by monitoring the E2-Ub thioester conjugate formation under non-reducing condition. Comparing to the E2 Screening Kit (Cat# J1100), this kit contains additional SUMO or Nedd8-activating E1, SUMO2 and Nedd8, which allow to assess SUMOylation and neddylation.