E2 ubiquitin conjugating enzymes are crucial components of the ubiquitin-proteasome system, which regulates protein degradation in cells. These enzymes facilitate the transfer of ubiquitin, a small protein, to target proteins, marking them for degradation or altering their function. This process is essential for maintaining cellular homeostasis and regulating various biological processes. E2 enzymes work in conjunction with E1 ubiquitin-activating enzymes and E3 ubiquitin ligases. While E1 activates ubiquitin, E2 enzymes carry it to E3, which determines the specific substrate for ubiquitination. This intricate system plays a vital role in processes such as cell cycle regulation, DNA repair, and immune response.