UCHL1 is a member of a gene family whose products hydrolyze small C-terminal adducts of ubiquitin to generate the ubiquitin monomer. Expression of UCHL1 is highly specific to neurons and to cells of the diffuse neuroendocrine system and their tumors. It is present in all neurons.

Human UCH-L1 and the closely related protein UCHL3 have the most complicated knot structure yet discovered for a protein, with five knot crossings. It is speculated that a knot structure may increase a protein's resistance to degradation in the proteasome.Ubiquitin carboxy-terminal hydrolase L1 has been shown to interact with COP9 constitutive photomorphogenic homolog subunit 5.