The present invention relates to the discovery of RNA 5′ polyphosphatase enzymes not previously described in the art, methods for discovery of said enzymes, compositions of said enzymes, methods for making said enzymes, and various methods and kits for using said enzymes for biomedical research, for human and non-human diagnostics, for production of therapeutic products, and for other applications. In particular, some embodiments provide compositions, kits and methods for employing RNA polyphosphatases for isolation, purification, production, and assay of capped RNA using a biological sample or a sample from an in vitro capping reaction wherein the sample also contains RNA that is not capped. Other embodiments provide compositions, kits and methods wherein RNA polyphosphatases comprise signal-amplifying enzymes for analyte-specific assays.