NCIt definition : Genes encoding enzymes that catalyze 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.;
NCIt note : The IUBMB has recategorized E2 ubiquitin-conjugating enzymes and E3 ubiquitin-protein
ligases as transferases (EC 2). Thus, E1, E2 and E3 enzymes may be considered part
of a ubiquitin ligase complex, but only E1 enzymes are categorized as ligases (EC
6).;