USP38 (ubiquitin specific peptidase 38), also known as HP43.8KD, is a 1,042 amino acid deubiquitinating enzyme that participates in the Ub pathway, exhibiting a preference towards 'Lys-63'-linked Ubiquitin chains. A member of the peptidase C19 family, the catalytic activity of USP38 involves a combination of the ubiquitin carboxyl-terminal thiolester and water to produce ubiquitin and a thiol. USP38 is highly expressed in skeletal muscle and adrenal gland.