Ubiquitin carboxyl-terminal hydrolase 13 (USP13) is a specialized cysteine protease with a predicted molecular weight of 97 kDa. USP13 is a member of the peptidase C19 family and the human protein shares 96% amino acid sequence identity with its mouse ortholog. Recombinant USP13 has weak deubiquitinase activity against unanchored polyubiquitin chains, but will disassemble tetraubiquitin chains in extended reactions, particularly K63 and K48 linkages. Suggested biological targets of USP13 include PTEN, BECN1, MITF, SKP2 and USP10, and roles for USP13 in melanoma and colorectal cancer have been reported. This recombinant protein contains a C-terminal 6-His tag.