Peptidase C19 contains ubiquitin hydrolases. They are intracellular peptidases that remove ubiquitin molecules from polyubiquitinated peptides by cleavage of isopeptide bonds. They hydrolyze bonds involving the carboxyl group of the C-terminal Gly residue of ubiquitin. The purpose of the de-ubiquitination is thought to be editing of the ubiquitin conjugates, which could rescue them from degradation, as well as recycling of the ubiquitin. The ubiquitin/proteasome system is responsible for most protein turnover in the mammalian cell, and with over 50 members, family C19 is one of the largest families of peptidases in the human genome [, ].This entry encompasses ubiquitin-specific hydrolase 1 (MEROPS identifier C19.019). It is required for deubiquitination of monoubiquitinated proteins involved in various DNA repair pathways and is a key regulator of DNA repair mechanisms []. Substrates include monoubiquitinated PCNA [], and components FANCD2 []and FANCI []of the Fanconi anemia pathway, a genetic disorder that resultsin the inability to monoubiquitinate these components [].
