Application Adenosine 5′ phosphosulfate (APS) is used as a substrate of ATP sulfurylase to complete a PP(i)-recycling loop for exponential ATP amplification in firefly luciferase ATP luminescence assay and other pyrophosphate regeneration-dependent detection assays. Other Notes Tandem Mass Spectrometry data independently generated by Scripps Center for Metabolomics is available to view or download in PDF. A5508.pdf Tested metabolites are featured on Scripps Center for Metabolomics METLIN Metabolite Database. To learn more, visit sigma.com/metlin.