Fluorescent substrates for poly(ADP-ribosyl) hydrolases

The post-translational modification (PTM) and signaling molecule poly(ADP-ribose) (PAR) has an impact on diverse biological processes. PTM is regulated by a series of ADP-ribosyl glycohydrolases (PARG enzymes) that cleave polymers and/or liberate monomers from their protein targets. Disclosed herein is a substrate for monitoring PARG activity, TFMU-ADPr, which directly reports on total PAR hydrolase activity via release of a fluorophore; this substrate has excellent reactivity, generality, stability, and usability. A second substrate, TFMU-IDPr, selectively reports on PARG activity only from the enzyme ARH3. Use of these probes in whole-cell lysate experiments has revealed a mechanism by which ARH3 is inhibited by cholera toxin. TFMU-ADPr and TFMU-IDPr are versatile tools for assessing small-molecule inhibitors in vitro and probing the regulation of ADP-ribosyl catabolic enzymes.