Responsible for the proteolytic processing of the amyloid precursor protein (APP) (PubMed:29325091). Cleaves at the N-terminus of the A-beta peptide sequence, between residues 671 and 672 of APP, leads to the generation and extracellular release of beta-cleaved soluble APP, and a corresponding cell-associated C-terminal fragment which is later released by gamma-secretase (PubMed:29325091). Cleaves CHL1 (PubMed:29325091). Broad endopeptidase specificity. Cleaves Glu-Val-Asn-Leu-|-Asp-Ala-Glu-Phe in the Swedish variant of Alzheimer's amyloid precursor protein. Inhibited by RTN3 and RTN4. Monomer. Interacts (via DXXLL motif) with GGA1, GGA2 and GGA3 (via their VHS domain); the interaction highly increases when BACE1 is phosphorylated at Ser-498. Interacts with RTN1; RTN2; RTN3 and RTN4; the interaction leads to inhibition of amyloid precursor protein processing (By similarity). Interacts with SNX6. Interacts with PCSK9. Interacts with NAT8 and NAT8B. Interacts with BIN1 (By similarity). Interacts (via extracellular domain) with ADAM10 (via extracellular domain) (PubMed:29325091). Interacts with SORL1; this interaction may affect binding with APP and hence reduce APP cleavage (PubMed:16407538). Predominantly localized to the later Golgi/trans-Golgi network (TGN) and minimally detectable in the early Golgi compartments. A small portion is also found in the endoplasmic reticulum, endosomes and on the cell surface (By similarity). Colocalization with APP in early endosomes is due to addition of bisecting N-acetylglucosamine wich blocks targeting to late endosomes and lysosomes (PubMed:25592972). Retrogradly transported from endosomal compartments to the trans-Golgi network in a phosphorylation- and GGA1- dependent manner (By similarity). Expressed in the brain, specifically in neurons and astrocytes (at protein level). In brain oxidative stress induced by amyloid-beta deposition during aging increases protein levels. DXXLL motif is required for a proper endocytosis and retrograde transport to the trans-Golgi network, as well as for regulation of lysosomal degradation. The transmembrane domain is necessary for its activity. It determines its late Golgi localization and access to its substrate, APP. N-Glycosylated (By similarity). Addition of a bisecting N-acetylglucosamine by MGAT3 blocks lysosomal targeting, further degradation and is required for maintaining stability under stress conditions (PubMed:25592972, PubMed:26467158). Palmitoylation mediates lipid raft localization. Acetylated in the endoplasmic reticulum at Lys-126, Lys-275, Lys-279, Lys-285, Lys-299, Lys-300 and Lys-307. Acetylation by NAT8 and NAT8B is transient and deacetylation probably occurs in the Golgi. Acetylation regulates the maturation, the transport to the plasma membrane, the stability and the expression of the protein. Ubiquitinated at Lys-501, ubiquitination leads to lysosomal degradation. Monoubiquitinated and 'Lys-63'-linked polyubitinated. Deubiquitnated by USP8; inhibits lysosomal degradation. Phosphorylation at Ser-498 is required for interaction with GGA1 and retrograded transport from endosomal compartments to the trans-Golgi network. Non-phosphorylated BACE1 enters a direct recycling route to the cell surface. Mice show a higher mortality rate early in life. Belongs to the peptidase A1 family.