ANTIBACTERIAL PEPTIDES ARE PRESENT IN CHROMAFFIN CELL SECRETORY GRANULES

1. Antibacterial activity has recently been associated with the solubl e matrix of bovine chromaffin granules. Furthermore, this activity was detected in the contents secreted from cultured chromaffin cells foll owing stimulation. 2. The agents responsible for the inhibition of Gra m+ and Gram-bacteria growth are granular peptides acting in the microm olar range or below. Ln secretory granules, these peptides are generat ed from cleavage of chromogranins and proenkephalin A and are released together with catecholamines into the circulation.3, Secretolytin and enkelytin are the best characterized; these two peptides share sequen ce homology and similar antibacterial activity with insect cecropins a nd intestinal diazepam-binding inhibitor. For some of the peptides der ived from chromogranin A, posttranslational modifications were essenti al since antibacterial activity was expressed only when peptides were phosphorylated and/or glycosylated. 4. The significance of this activi ty is not yet understood. It may be reminiscent of some primitive defe nse mechanism or may serve as a first barrier to bacteria infection du ring stress, as these peptides are secreted along with catecholamines.