(Ac-ANW)2R110

(Ac-ANW)2R110 is a selective fluorogenic substrate for proteasome 20S-beta 5i. The non-fluorescent substrate generates a bright green fluorescent rhodamine 110 product that has an emission spectra that can be easily detected with a FITC filter set. This rhodamine 110 substrate is much more sensitive than the AMC-, AFC- or 4-nitroaniline-based substrates. The most common form of the proteasome is known as the 26S proteasome that contains one 20S core particle structure and two 19S regulatory caps. All 20S particles consist of four stacked heptameric ring structures that are themselves composed of two different types of subunits; alpha subunits are structural in nature, whereas beta subunits are predominantly catalytic. The outer two rings in the stack consist of seven alpha subunits each, which serve as docking domains for the regulatory particles and the alpha subunits N-termini form a gate that blocks unregulated access of substrates to the interior cavity. The inner two rings each consist of seven beta subunits and contain the protease active sites that perform the proteolysis reactions. In mammals, the beta1, beta2, and beta5 subunits are catalytic. Although they share a common mechanism, they have three distinct substrate specificities considered chymotrypsin-like, trypsin-like, and peptidyl-glutamyl peptide-hydrolyzing. Alternative beta forms denoted beta 1i, beta 2i, and beta 5i can be expressed in hematopoietic cells in response to exposure to pro-inflammatory signals such as cytokines, in particular, interferon gamma.