UBE2E1 belongs to the E2 ubiquitin-conjugating enzyme family. UBE2E1 accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. UBE2E1 catalyzes the covalent attachment of ISG15 to other proteins. UBE2E1 mediates the selective degradation of short-lived and abnormal proteins. In vitro, UBE2E1 also catalyzes ’Lys-48’-linked polyubiquitination.