Ubiquitin-like modifier activating enzyme 5（UBA5) is a member of the ubiquitin-activating E1 family and UBA5 subfamily. Ubiquitin and ubiquitin-like proteins are recognized as covalently conjugated to various cellular substrates by a three-step enzymatic pathway. The ubiquitin-activating enzyme（E1) has a vital role in the first step of ubiquitination pathway to activate ubiquitin or ubiquitin-like proteins. UBA5 activates an ubiquitin-like protein， ubiquitin-fold modifier 1（Ufm1)， by forming a high-energy thioester bond. UBA5 is located primarily in cytoplasm， while it generally localizes to the nucleus in presence of SUMO2.
