OTU1 (Ubiquitin thioesterase OTU1, also known as YOD1) is a deubiquitinating enzyme of the ovarian tumor (otubain, also known as "Otu") family. YOD1 is part of a multi-protein complex containing p97, suggesting this deubiquitinase may function in the endoplasmic reticulum-associated degradation (ERAD) of misfolded lumenal proteins. A possible role for YOD1 is the trimming of polyubiquitin chains from substrates to facilitate their threading through the VCP/p97 pore. YOD1 is capable of hydrolyzing K6-, K11-, K27-, K29-, and K33-linked polyubiquitin chains.