Intact proenkephalin is the major enkephalin-containing peptide produced in rat adrenal glands after denervation.

We have shown previously that enkephalin-containing peptides of high molecular weight increase 10- to 15-fold 3 days after adrenal denervation and have suggested that much of this material may represent newly synthesized proenkephalin. In this paper we report that most of the material appearing after denervation is indeed intact proenkephalin. The putative proenkephalin was partially purified by gel filtration chromatography and HPLC. A molecular size of about 25 kDa was estimated by gel filtration. On HPLC, the putative proenkephalin was eluted at a much higher propanol concentration than the 18.2-kDa enkephalin-containing peptide isolated previously. Treatment of this putative proenkephalin with endoproteinase Lys-C showed it contain [Met]-enkephalin, [Leu]enkephalin, [Met]enkephalin-Arg6-Phe7, and [Met]enkephalin-Arg6-Gly7-Leu8 in the same ratios as are found in proenkephalin as deduced from sequencing of proenkephalin cDNA.