Beta-secretase 1

Beta-secretase 1 (BACE1), also known as beta-site amyloid precursor protein cleaving enzyme 1, beta-site APP cleaving enzyme 1, membrane-associated aspartic protease 2, memapsin-2, aspartyl protease 2, and ASP2, is an enzyme that in humans is encoded by the BACE1 gene.

BACE1 is an aspartic-acid protease important in the formation of myelin sheaths in peripheral nerve cells. The transmembrane protein contains two active site aspartate residues in its extracellular protein domain and may function as a dimer.

Role in Alzheimer's disease

Generation of the 40 or 42 amino acid-long amyloid-β peptides that aggregate in the brain of Alzheimer's patients requires two sequential cleavages of the amyloid precursor protein (APP). Extracellular cleavage of APP by BACE1 creates a soluble extracellular fragment and a cell membrane-bound fragment referred to as C99. Cleavage of C99 within its transmembrane domain by γ-secretase releases the intracellular domain of APP and produces amyloid-β. Since alpha-secretase cleaves APP closer to the cell membrane than BACE1 does, it removes a fragment of the amyloid-β peptide. Initial cleavage of APP by alpha-secretase rather than BACE1 prevents eventual generation of amyloid-β.