Ubiquitin activating enzymes, also known as E1 enzymes, regulate the ubiquitin-proteasome system (UPS), a pathway responsible for regulating protein degradation, DNA repair, and various cell signalling processes. E1 enzymes initiate the ubiquitylation process by activating the ubiquitin molecules and transferring them to ubiquitin-conjugating enzymes (E2 enzymes). UBA1 (Ubiquitin-Like Modifier Activating Enzyme 1) is the primary E1 enzyme responsible for initiating the ubiquitylation cascade in humans. In the presence of ATP, UBA1 catalyses the adenylation of the C-terminus of ubiquitin. This results in the formation of a high-energy thioester bond between the C-terminal glycine of ubiquitin and the phosphate group of AMP (adenosine monophosphate). This step activates ubiquitin for subsequent transfer. UBA1 then transfers the activated ubiquitin from the E1-ubiquitin thioester intermediate to an E2 enzyme (ubiquitin-conjugating enzyme). The E2 enzyme contains its own active site cysteine residue. UBA1 has a high specificity for ubiquitin but can also activate other ubiquitin-like modifiers (UBLs), such as NEDD8 and ISG15. UBA1 activates ubiquitin, which is subsequently transferred to ubiquitin-conjugating enzymes (E2s), such as UBE2D1 (also known as UbcH5a), for further ubiquitin chain assembly. UBA6 (Ubiquitin-Like Modifier Activating Enzyme 6) is another E1 enzyme involved in the activation of ubiquitin, specifically in the context of the ubiquitin-like modifier FAT10 (HLA-F adjacent transcript 10). UBA6 is unique in its ability to activate FAT10, which has functions related to immune regulation and cellular stress responses. UBA6 activates FAT10, leading to its conjugation to target proteins. The functional consequences of FAT10ylation are not fully understood but may also involve proteasomal degradation of modified proteins. ATG7 (Autophagy-Related E1-Like Enzyme) serves as an E1-like enzyme in the autophagy pathway, the cellular process that degrades damaged organelles and protein aggregates. ATG7 activates ATG8 family proteins, such as LC3 (Microtubule-associated protein 1A/1B-light chain 3), by forming thioester bonds with them. ATG7 activates LC3, which is subsequently conjugated to phosphatidylethanolamine (PE) to form LC3-II. LC3-II is key for autophagosome formation and cargo recognition during autophagy. SUMO E1 (SUMO Activating Enzyme), which includes SAE1 and SAE2 subunits, initiates the SUMOylation process by activating Small Ubiquitin-like Modifier (SUMO) proteins. SUMO E1 enzymes are specific to SUMO proteins and form thioester bonds with SUMO at its C-terminal glycine residue. SUMO E1 activates SUMO proteins, which are then transferred to ubiquitin-conjugating enzymes (E2s) and subsequently conjugated to target proteins, modulating various cellular processes such as DNA repair and protein localization. UFM1 E1 (Ubiquitin-Fold Modifier 1 Activating Enzyme), composed of UBA5 and UFC1 subunits, is involved in UFM1ylation, a process like ubiquitination and SUMOylation. UFM1 E1 activates UFM1, a ubiquitin-like modifier that regulates protein trafficking and quality control. UFM1 E1 activates UFM1, which is subsequently conjugated to target proteins involved in endoplasmic reticulum function and cellular homeostasis. Thus, ubiquitin activating E1 enzymes play initiating roles in post-translational modification pathways that regulate a wide range of cellular processes. The specificity of each E1 enzyme for its respective ubiquitin-like modifier ensures precise control over these diverse cellular functions. Explore our full E1 ubiquitin activating enzymes product range below and discover more, for less.