Enkephalin biosynthetic pathway: a 5300-dalton adrenal polypeptide that terminates at its COOH end with the sequence [Met]enkephalin-Arg-Gly-Leu-COOH.

An enkephalin-containing polypeptide of 5300 daltons has been isolated from extracts of bovine adrenal medulla and purified to homogeneity, and its sequence has been determined by a combination of automated Edman degradation and enzymatic time-course hydrolysis. The polypeptide contains a single [Met]enkephalin sequence followed by Arg-Gly-Leu-COOH, which forms the COOH terminus of the molecule. The enkephalin sequence is preceded by a Lys-Arg linkage, typical of prohormone cleavage sites. Posttranslational processing of the polypeptide at this site would lead to release of the octapeptide [Met]enkephalin-Arg6-Gly7-Leu8.