SAE1(SUMO1 activating enzyme subunit 1) also known as AOS1, UBL1E1 is a crucial component of the ubiquitin-like (UBL) conjugation pathway, specifically functioning as a ubiquitin-activating E1 ligase. SAE1 plays a vital role in the activation of UBL1, which is essential for various cellular processes, including cell cycle regulation and stress response mechanisms. SAE1 operates as a dimeric enzyme, facilitating the ATP-dependent activation of UBL1, and can form heterodimers with UBLE1A and UBLE1B, enhancing functional capacity. Proper functioning of SAE1 is critical, as disruptions in the UBL conjugation pathway can lead to various diseases, including cancer and neurodegenerative disorders.