Proenkephalin B (Prodynorphin)-Derived Opioid Peptides: Evidence for a Differential Processing in Lobes of the Pituitary

Abstract

The distribution of peptides derived from the novel opioid peptide precursor proenkephalin B (prodynorphin) was studied in lobes of the rat pituitary with antibodies against .alpha.-neoendorphin (.alpha.-neo-E) .beta.-neoE, dynorphin (DYN)-(1-17), DYN-(1-8), and DYN B in combination with gel filtration and high pressure liquid chromatography. In the posterior pituitary, all 5 opioid peptides occurred in high and about equimolar ion concentrations, whereas putative precursor peptides were found in only minor quantities. In the anterior pituitary immunoreactive (ir-) DYN-(1-17) and ir-DYN B consisted of exclusively of a common precursor species with a MW of about 6000. Six thousand-dalton DYN may be comprised of the C-terminal portion of proenkephalin B, with the sequence of DYN-(1-17) at its N-terminus. The major portions of ir-.alpha.-neo-E and ir-.beta.-neoE in the anterior pituitary were of MW of 8000. A disoriental processing of the opioid peptide precursor proenkephalin B in the 2 lobes of the pituitary may occur. The anterior pituitary seems to process proenkephalin B predominantly into high MW forms of neo-E and DYN, whereas in the posterior pituitary proenkephalin B undergoes further proteolytic processing to the smaller opioid peptides .alpha.-neo-E, .beta.-neo-E, DYN-(1-17), DYN-(1-8), and DYN B. Thus, processing differences may enable the selective liberation of different (opioid) peptide with distinct biological properties from 1 precursor within different tissues.