Ubiquitin carboxyl-terminal hydrolase isozyme L5 (UCHL5) belongs to the peptidase C12 family. This protein is protease that specifically cleaves 'Lys-48'-linked polyubiquitin chains, and deubiquitinating enzyme associated with the 19S regulatory subunit of the 26S proteasome. Recombinant human UCHL5 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.