High Quality Content by WIKIPEDIA articles! Alpha-synuclein is a protein that, in humans, is encoded by the SNCA gene. An alpha-synuclein fragment, known as the non-Abeta component (NAC) of Alzheimer`s disease amyloid, originally found in an amyloid-enriched fraction, is shown to be a fragment of its precursor protein, NACP, by cloning of the full-length cDNA. It was later determined that NACP was the human homologue of Torpedo synuclein. Therefore, NACP is now referred to as human alpha-synuclein.