The DUB-Glo™ Protease Assay provides a luminescent substrate, Z-RLRGG-aminoluciferin, in a reagent optimized for protease and luciferase activity. The RLRGG sequence is the C-terminal pentapeptide of ubiquitin.
Hi Jingjing, as far as I can tell Z= Cbz-Arg-Leu-Arg-Gly-Gly-7-amino-4-methylcoumarin, where Cbz is Carboxybenzyl (abbreviated as Z), a carbamate which is often used as an amine protecting group in organic synthesis.