aminoacyltransferase activity ubiquitin-like protein transferase activity ubiquitin-like-protein ligase activity small conjugating protein transferase activity molecular_function small protein conjugating enzyme activity E2 Catalysis of the transfer of a ubiquitin-like from one protein to another via the reaction X-ULP + Y = Y-ULP + X, where both X-ULP and Y-ULP are covalent linkages. ULP represents a ubiquitin-like protein. GO:0008639 ubiquitin-like conjugating enzyme activity small conjugating protein ligase activity Reactome:R-HSA-688137 Reactome:R-HSA-5678490 GO:0008640 GO:0019787 E3 catalytic activity, acting on a protein