E1-like enzyme which specifically catalyzes the second step in ufmylation (PubMed:15071506, PubMed:29868776). Accepts the ubiquitin-like modifier UFM1 from the E1 enzyme UBA5 and forms an intermediate with UFM1 via a thioester linkage (PubMed:15071506, PubMed:29868776). Ufmylation is involved in reticulophagy (also called ER-phagy) induced in response to endoplasmic reticulum stress (PubMed:32160526).
