Ac-Nle-Pro-Nle-Asp-AMC is a substrate for proteasomes that is cleaved by the caspase-like site, also known as postglutamyl peptide hydrolase (PGPH), with specific activities of 113 and 6.6 nmol/min/mg by the 26S (rabbit muscle) and 20S (yeast) proteasomes, respectively.1 Caspase-like activity can be quantified by fluorescent detection of free AMC (also known as 7-amino-4-methylcoumarin), which is excited at 340-360 nm and emits at 440-460 nm. Ac-Nle-Pro-Nle-Asp-AMC inhibits the chymotrypsin-like activity of the proteasome allosterically when bound to the caspase-like site.1 It has been used to determine L-DOPA's effects on protein turnover rates.2
1.Kisselev, A.F., Garcia-Calvo, M., Overkleeft, H.S., et al.The caspase-like sites of proteasomes, their substrate specificity, new inhibitors and substrates, and allosteric interactions with the trypsin-like sitesThe Journal of Biological Chemisty278(38)35869-35877(2003) 2.Dunlop, R.A., Dean, R.T., and Rodgers, K.J.The impact of specific oxidized amino acids on protein turnover in J774 cellsBiochem J.410(1)131-140(2008)