Enkephalin biosynthesis in the adrenal medulla.

Although the number of enkephalin-containing polypeptides (ECP's) from bovine adrenal chromaffin granules have been isolated and sequenced the complete sequence of the translation product has not been determined. Preliminary data from cDNA suggests a 1500 mRNA is the precursor mRNA. Continuation of that line of research to clone the cDNA should provide the total precursor amino acid sequence. Data obtained from ovine chromaffin granules indicates that the ECP's from the species are very similar to those in bovine granules. If this is extended to other species it would appear that some of the ECP's may serve a role beyond that of an enkephalin precursor. In an analogy to pro-opiocortin the "proenkephalin" also may contain multiple hormone sequences. The sequences determined thus far imply trypsin-like enzymes and a carboxy-peptidase B are used to cleave the precursor. We have determined that both types of enzymes are indeed present in chromaffin granules and further studies of these enzymes will provide information of how the precursor cleavages are regulated.