Ubiquitylation is catalyzed by the sequential action of ubiquitinactivating enzyme (E1), a ubiquitin-conjugating enzyme (E2) and a ubiquitin protein ligase (E3). Ubiquitylation is essential to numerous cellular and developmental processes, including protein quality control, growth, apoptosis, antigen presentation, DNA repair, and signal transduction. PYR-41, 4[4-(5-nitro-furan-2-ylmethylene)-3,5-dioxo-pyrazolidin-1-yl]-benzoic acid ethyl ester, is a selective inhibitor of Ubiquitin-Activating Enzyme (E1).In vitro: In addition to blocking ubiquitylation, PYR-41 was found to increase total sumoylation in cells. PYR-41 could attenuate cytokine-mediated nuclear factor-KBactivation. This correlated with inhibition of nonproteasomal ubiquitylation of TRAF6, which is important to IKBkinase activation. Other sizes are also available. Please inqury us for quote.