Synaptophysin (also referred to as SVP38 and p38) is an acidic Ca2+ binding glycoprotein of about 38 kDa which exist largely in synaptic vesicles. It has 4 transmembrane regions and is reported to be a major cholesterol-binding protein in synaptic vesicles. Synaptophysin may regulate synaptic exocytosis by competing with proteins such as SNAP25 and syntaxins to bind to synaptobrevin (vesicle-associated membrane protein, or VAMP). It may also participate in synaptic endocytosis, which contributes to rapid recycling of synaptic vesicle.Synonyms: Major synaptic vesicle protein p38, Neuroendocrine Marker