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. Interacts with UBA5 (via C-terminus). Interacts with UFL1. Interacts with KIRREL3. Interacts with UFM1. Belongs to the ubiquitin-conjugating enzyme family. UFC1 subfamily.