obsolete ubiquitin cycle true This term was made obsolete because it implies that every protein that is ubiquitinated is also subsequently deubiquinitated, which is not true. Also, the process ontology does not include analogous terms for other small modifiers. OBSOLETE. The cyclical process by which one or more ubiquitin groups are added to (ubiquitination) and removed from (deubiquitination) a protein. GO:0006512 biological_process ubiquitin cycle