Proenkephalin A 119–159, a stable proenkephalin A precursor fragment identified in human circulation

In this report, we describe a newly developed sandwich immunoassay using antibodies against the proenkephalin A 119–159 peptide (PENK A 119–159). PENK A 119–159 immunoreactivity was detectable in the circulation of human blood donors and in cerebrospinal fluid (CSF) of patients without a neurologic disorder. The concentration was about 100 times higher in CSF than in serum. Analytical reversed phase HPLC revealed that PENK A 119–159 is the main immunoreactivity in human circulation and CSF. Moreover, PENK A 119–159 is stable in vitro for at least 48 h at room temperature as compared to the low stability of the peptides methionine- and leucine-enkephalin. This suggests the use of PENK A 119–159 measurement as surrogate molecule for the release of the mature peptides derived from proenkephalin A.