Fluor de Lys®-SIRT1 is a fluorogenic, acetylated peptide substrate for SIRT1 (human Sirtuin 1). Based on residues 379-382 of p53 (Arg-His-Lys-Lys(Ac)), a site of regulatory acetylation by the p300 and CBP acetyltransferases (lysines 381, 382), it was the best substrate for SIRT1 from among a panel of substrates patterned on p53, histone H3, and histone H4 acetylation sites. Fluor de Lys®-SIRT1 is deacetylated by SIRT1 (BML-SE239) at a rate of more then 8-fold that of the acetylated lysine substrate, Fluor de Lys® (Prod. No. BML-KI104; acetylated substrates both at 25 µM, 500 µM NAD+). The Km of Fluor de Lys®-SIRT1 for human recombinant Sirtuin 1 is 108 µM (determined at 37°C, 500 µM NAD+). Must be used in conjunction with Fluor de Lys® Developer II (Prod. No. BML-KI176). Fluorescent signal indicates deacetylation of Lys382. Sufficient for 100-200 assays of human recombinant SIRT1 (1U/well, 50-100 µM substrate).