Strongly inhibits glucose induced insulin release from the pancreas. Catestatin 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. Serpinin 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 (By similarity). Serpinin and pGlu-serpinin can enhance both myocardial contractility (inotropy) and relaxation (lusitropy) and this cardio-stimulation requires a beta 1-adrenergic receptor/adenylate cyclase/cAMP/PKA pathway (PubMed:22459152). Interacts with SCG3; this interaction is optimal in conditions mimicking the lumenal milieu of the trans-Golgi network, i.e. pH 5.5 and 10 mM Ca(+2). 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. Pyroglutaminated serpinin localizes to secretory vesicle. Expressed in the brain and adrenal and pituitary glands. CgA is O-glycosylated. Binds calcium with a low-affinity. Belongs to the chromogranin/secretogranin protein family.