The function of DOC2B (double C2 domain beta, ENSG00000272636) is as follows. Calcium sensor which positively regulates SNARE-dependent fusion of vesicles with membranes. Binds phospholipids in a calcium- dependent manner and may act at the priming stage of fusion by modifying membrane curvature to stimulate fusion. Involved in calcium- triggered exocytosis in chromaffin cells and calcium-dependent spontaneous release of neurotransmitter in absence of action potentials in neuronal cells. Involved both in glucose-stimulated insulin secretion in pancreatic cells and insulin-dependent GLUT4 transport to the plasma membrane in adipocytes (By similarity). {ECO:0000250, ECO:0000269|PubMed:9804756}.