Deubiquitinating enzymes (DUBs) are proteases that posses the ability to cleave ubiquitin chains or the isopeptide bond that conjugates ubiquitin with a substrate. Human cells have approximately 100 DUBs that play important roles in regulating various cellular events. A20 downregulates the NF-κB pathway and proinflammatory gene expression in cells such as macrophages.The N-terminal domain of A20 contains the DUB activity.