Sirtuins are NAD-dependent lysine deacylases that play critical roles in 
cellular regulation and are implicated in human diseases. Modulators of sirtuins 
are needed as tools for investigating their biological functions and possible 
therapeutic applications. However, the discovery of sirtuin modulators is 
hampered by the lack of efficient sirtuin assays. Here we report an improved 
fluorogenic assay for SIRT1, SIRT2, and SIRT3 using a new substrate, a myristoyl 
peptide with a C-terminal aminocoumarin. The new assay has several advantages, 
including significantly lower substrate concentration needed, increased 
signal-to-background ratio, and improved Z'-factor. The novel assay thus will 
expedite high-throughput screening of SIRT1, SIRT2, and SIRT3 modulators.