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 (PubMed:15326220). Displays antibacterial activity against Gram-positive bacteria S.aureus and M.luteus, and Gram-negative bacteria E.coli and P.aeruginosa (PubMed:15723172 and PubMed:24723458). Can induce mast cell migration, degranulation and production of cytokines and chemokines (PubMed:21214543). Acts as a potent scavenger of free radicals in vitro (PubMed:24723458). May play a role in the regulation of cardiac function and blood pressure (PubMed:18541522). 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. GE-25 is found in the brain. Sulfated on tyrosine residues and/or contains sulfated glycans. O-glycosylated with core 1 or possibly core 8 glycans. Proteolytic processing gives rise to an additional longer form of catestatin (residues 358-390) which displays a less potent catecholamine release-inhibitory activity (PubMed:10781584). Plasmin-mediated proteolytic processing can give rise to additional shorter and longer forms of catestatin peptides (PubMed:17991725). Binds calcium with a low-affinity. Belongs to the chromogranin/secretogranin protein family.