E1 Ubiquitin-Activating Enzyme

**Semantic type:** Amino Acid, Peptide, or Protein|Enzyme

**Definition:** A ligase that catalyzes the first step in the ubiquitination reaction via the ligation of the C-terminal lysine of ubiquitin to the E1 enzyme in an ATP-dependent reaction.

**Synonyms:** - EC 6.2.1.45 - EC 6.3.2.19, Formerly - Ubiquitin-Activating Enzyme