E1-like enzyme which specifically catalyzes the second step in ufmylation (, ). Accepts the ubiquitin-like modifier UFM1 from the E1 enzyme UBA5 and forms an intermediate with UFM1 via a thioester linkage (, ). Ufmylation is involved in reticulophagy (also called ER-phagy) induced in response to endoplasmic reticulum stress .