Strongly inhibits glucose induced insulin release from the pancreas. Inhibits catecholamine release from chromaffin cells and noradrenergic neurons by acting as a non-competitive nicotinic cholinergic antagonist. Can induce mast cell migration, degranulation and production of cytokines and chemokines. Regulates granule biogenesis in endocrine cells by up-regulating the transcription of protease nexin 1 (SERPINE2) via a cAMP-PKA-SP1 pathway. This leads to inhibition of granule protein degradation in the Golgi complex which in turn promotes granule formation. Interacts with SCG3. Pyroglutaminated serpinin localizes to secretory vesicle. Associated with the secretory granule membrane through direct interaction to SCG3 that in turn binds to cholesterol-enriched lipid rafts in intragranular conditions. In pituitary gonadotropes, located in large secretory granules. Highly expressed in adrenal medulla and pituitary gland. Weaker expression detected in cerebrum, cerebellum, spinal cord, liver, thyroid gland, striated muscle, lung, spleen, kidney, parotid gland, and sublingual gland. O-glycosylated. Binds calcium with a low-affinity. Belongs to the chromogranin/secretogranin protein family.