E2 enzymes, also known as ubiquitin-conjugating enzymes, play a crucial role in the process of protein ubiquitination. This process involves attaching a small protein called ubiquitin to target proteins, marking them for degradation or altering their function. E2 enzymes work in conjunction with E1 enzymes, which activate ubiquitin, and E3 enzymes, which transfer ubiquitin to the target protein. These enzymes are essential for maintaining cellular homeostasis and regulating various biological processes, including cell cycle progression, DNA repair, and signal transduction. Dysregulation of E2 enzymes can lead to various diseases, including cancer and neurodegenerative disorders.