URM1 is ubiquitin-related modifier 1 homolog protein which mainly functions in the post-translational modification of proteins via the urmylation pathway. Urm1 covalently binds to its E1 activating enzyme， Uba4p， to conjugate alkyl hydroperoxide reductase （Ahp1） as determined by studies with Saccharomyces cerevisiae. It has been theorized that this complex may then have a role in the oxidative-stress response in mammals.
