Ubiquitin ligases are enzymes that play a crucial role in the process of protein degradation within cells. They facilitate the attachment of a small protein called ubiquitin to target proteins, marking them for destruction by the proteasome. This process is essential for regulating various cellular functions, including the removal of damaged or misfolded proteins. There are three main types of ubiquitin ligases: E1 (ubiquitin-activating enzymes), E2 (ubiquitin-conjugating enzymes), and E3 (ubiquitin ligases). The E3 ligases are particularly important because they determine the specificity of the ubiquitination process, ensuring that the right proteins are tagged for degradation based on cellular needs.