Regulation of deubiquitinase proteolytic activity.

Deubiquitinases (DUBs) are proteolytic enzymes whose function is to oppose the process of the conjugation of ubiquitin to a specific substrate. This task is accomplished through an enzymatic cascade involving E1, E2, and E3 enzymes, which collectively produce a product that is either monoubiquitinated, or polyubiquitinated with multiple single ubiquitins or with ubiquitin chains. The resulting modifications may impact protein function or may lead to the degradation of the ubiquitinated species, so the removal of such modifications must be tightly regulated. On the basis of recent work featuring crystal structures and detailed biochemical or biophysical studies of DUBs, we will discuss here how posttranslational modifications, protein binding partners, and reactive oxygen species regulate their catalytic activity.