Protein turnover is vital to cellular homeostasis. Many proteins are degraded efficiently only after they have been post-translationally "tagged" with a polyubiquitin chain. Ubiquitylation is a form of Post-Translational Modification (PTM): addition of a ubiquitin to the chain is catalyzed by E3 ligases. and removal of ubiquitin is catalyzed by a De-UBiquitylating enzyme (DUB). https://www.ealisboa.com/quick-save-Pentair-Female-to-Female-Hose-Adapter-4-For-Sectional-Hose-K21241B-top-mega/