Proenkephalin and the Products of Its Processing: Chemistry and Biology

Publisher Summary This chapter describes the chemistry of proenkephalin and the products of its processing. The purpose of studies described in the chapter was to characterize the EC peptides in the chromaffin granules and compare them with the β-endorphin-related products from the anterior pituitary gland. In what subsequently became a general procedure, purified chromaffin granules from approximately 25–50 bovine adrenal medullas were homogenized in acid in the presence of protease inhibitors, and the extracts were applied to the Sephadex G-100 column. The active peptides were arbitrarily divided into five fractions corresponding to MT values of approximately, 20,000, 10,000 to 15,000, 5000, 2000 to 5000, and < 1000. Under some conditions of extraction, an even larger EC peptide was observed eluting from a Sephadex G-150 column as a peak with an MT of about 40,000 to 50,000. Opiate activity in fractions I and II appeared only when the material was digested with trypsin prior to assay. The opiate activity of peak III was also greatly enhanced by trypsin digestion. Some increases in activity were also observed on incubating peaks IV and V with trypsin.