Ready-to-use ELISA kits are available for the detection of Met Enkephalin, an alias of the protein, proenkephalin. The official gene symbol is PENK. The kits can detect several species variants of the protein, including: human, mouse, rat, and bovine. The protein, with a mass of 30.8 kDa and length of 267 residues, is reported to be secreted. It is a member of the Opioid neuropeptide precursor family and may be known by other names, including: preproenkephalin, peptide F, enkephalin A, and proenkephalin-A.