IUBMB Enzyme Nomenclature


Accepted name: HECT-type E3 ubiquitin transferase

Reaction: [E2 ubiquitin-conjugating enzyme]-S-ubiquitinyl-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-N6-ubiquitinyl-L-lysine (overall reaction)
(1a) [E2 ubiquitin-conjugating enzyme]-S-ubiquitinyl-L-cysteine + [HECT-type E3 ubiquitin transferase]-L-cysteine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + [HECT-type E3 ubiquitin transferase]-S-ubiquitinyl-L-cysteine
(1b) [HECT-type E3 ubiquitin transferase]-S-ubiquitinyl-L-cysteine + [acceptor protein]-L-lysine = [HECT-type E3 ubiquitin transferase]-L-cysteine + [acceptor protein]-N6-ubiquitinyl-L-lysine

Glossary: HECT protein domain = Homologous to the E6-AP Carboxyl Terminus protein domain

Other name(s): HECT E3 ligase (misleading); ubiquitin transferase HECT-E3; S-ubiquitinyl-[HECT-type E3-ubiquitin transferase]-L-cysteine:acceptor protein ubiquitin transferase (isopeptide bond-forming)

Systematic name: [E2 ubiquitin-conjugating enzyme]-S-ubiquitinyl-L-cysteine:[acceptor protein] ubiquitin transferase (isopeptide bond-forming)

Comments: In the first step the enzyme transfers ubiquitin from the E2 ubiquitin-conjugating enzyme (EC to a cysteine residue in its HECT domain (which is located in the C-terminal region), forming a thioester bond. In a subsequent step the enzyme transfers the ubiquitin to an acceptor protein, resulting in the formation of an isopeptide bond between the C-terminal glycine residue of ubiquitin and the ε-amino group of an L-lysine residue of the acceptor protein. cf. EC, RING-type E3 ubiquitin transferase and EC, RBR-type E3 ubiquitin transferase.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number:


1. Maspero, E., Mari, S., Valentini, E., Musacchio, A., Fish, A., Pasqualato, S. and Polo, S. Structure of the HECT:ubiquitin complex and its role in ubiquitin chain elongation. EMBO Rep. 12 (2011) 342-349. [PMID: 21399620]

2. Metzger, M.B., Hristova, V.A. and Weissman, A.M. HECT and RING finger families of E3 ubiquitin ligases at a glance. J. Cell Sci. 125 (2012) 531-537. [PMID: 22389392]

[EC created 2015, modified 2017]

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