Another recently identified enzyme exhibiting α-secretase activity is BACE2, a single transmembrane aspartyl protease of 518 amino acids. The coding sequences of BACE2 and the β-secretase-encoding BACE1 are about ∼50% identical. Despite extensive studies about the function of BACE1, the function of BACE2 remains unknown. Studies show that BACE2 cleaves APP at the Phe 19 and Phe 20 sites, which are adjacent to the α-secretase cleavage site, suggesting that BACE2 functions as an alternative α-secretase and as an antagonist of BACE1 (Farzan et al., 2000).
