Two adrenal opioid polypeptides: proposed intermediates in the processing of proenkephalin.

Abstract

Two enkephalin-containing polypeptides of 3600 and 4900 daltons were isolated from extracts of bovine adrenal medulla, purified to homogeneity, and analyzed by a combination of automated Edman degradation and enzymatic time course hydrolysis. The 4900 dalton polypeptide contains 2 copies of enkephalin: one an internal [Met]enkephalin sequence, the other a [Leu]enkephalin sequence at the carboxyl terminus. Sequence analysis of the 3600 dalton polypeptide was not completed, but the polypeptide contains a single [Met]enkephalin sequence followed by an -Arg-Phe linkage that forms the carboxyl terminus of the molecule. The above enkephalin-containing polypeptides may be intermediates in the biosynthesis of the enkephalins and they may be generated by posttranslational processing from a large multivalent enkephalin precursor molecule, proenkephalin. The term multivalent is used to indicate a polypeptide with many identical functional sequences.