Assays and probes with enzyme labels

This invention relates to probes comprising enzyme labels and specific binding members such as antibodies and single-stranded nucleic acids, and assays employing such probes. Probes comprise S1 and P1 nuclease (as an enzyme label) linked to a specific binding member such as a nucleotide sequence or an antibody. Such probes are useful for sandwich assays. As compared with known probes using alkaline phosphatase as a label, advantages include relative insensitivity to phosphate and elevated temperature and reduced risk of nonspecific binding.