| Category | Feature | Key details for human BACE1 | Evidence |
|---|---|---|---|
| Protein structure | Protein class and size | BACE1 is a type I membrane protein/type I transmembrane aspartyl protease encoded as a 501 aa preprotein in human; it belongs to the BACE1/BACE2 subfamily of membrane-anchored aspartyl proteases. (pqac-00000002, pqac-00000010) | (pqac-00000002, pqac-00000010) |
| Protein structure | Domain organization | Reported domain architecture includes signal peptide (aa 1-23), propeptide (aa 23-47), catalytic ectodomain (aa 47-454), transmembrane domain (aa 454-478), and cytosolic tail (aa 478-501). (pqac-00000010) | (pqac-00000010) |
| Protein structure | Maturation | The signal peptide directs trafficking to the ER; pro-domain removal by furin yields mature BACE1; maturation/activation occurs along the secretory pathway including the late Golgi/TGN. (pqac-00000002, pqac-00000012) | (pqac-00000002, pqac-00000012) |
| Catalytic mechanism | Catalytic residues | Protease activity depends on two catalytic aspartates, D93 and D289, in the ectodomain active site. (pqac-00000002) | (pqac-00000002) |
| Catalytic mechanism | Structural element regulating catalysis | An antiparallel hairpin flap (reported around Y128-G138) regulates access/positioning of substrate at the catalytic site and is a key determinant of inhibitor binding and catalysis. (pqac-00000010) | (pqac-00000010) |
| Catalytic mechanism | pH optimum | BACE1 functions best in acidic compartments; reported optimal activity is around pH 4.5 and highest activity is detected in acidic compartments such as endosomes and the trans-Golgi/endolysosomal system. (pqac-00000002, pqac-00000008, pqac-00000012) | (pqac-00000002, pqac-00000008, pqac-00000012) |
| Catalytic mechanism | Primary enzymatic reaction | In the amyloidogenic pathway, BACE1 performs the initial, rate-limiting β-site cleavage of APP to release sAPPβ and generate the membrane-bound C99/CTFβ fragment, which is then processed by γ-secretase to Aβ peptides. (pqac-00000005, pqac-00000008, pqac-00000012) | (pqac-00000005, pqac-00000008, pqac-00000012) |
| Catalytic mechanism | Substrate specificity | APP is an established substrate, but BACE1 has relatively loose sequence specificity and cleaves numerous type I membrane proteins; reviews note APP is actually a relatively poor substrate compared with the broader BACE1 substrate repertoire. (pqac-00000008, pqac-00000002) | (pqac-00000008, pqac-00000002) |
| Catalytic mechanism | Additional cleavage mode | Beyond β-site cleavage of APP, BACE1 can also cleave longer Aβ species at the β34-site to generate non-toxic Aβ34, supporting an amyloidolytic as well as amyloidogenic role. (pqac-00000008) | (pqac-00000008) |
| Subcellular localization | Secretory pathway | Newly synthesized BACE1 traffics through ER and Golgi/TGN; its localization to late Golgi/TGN is important for maturation and for limiting or enabling contact with APP. (pqac-00000002, pqac-00000011, pqac-00000012) | (pqac-00000002, pqac-00000011, pqac-00000012) |
| Subcellular localization | Plasma membrane and endocytic route | BACE1 is transported from the TGN to the plasma membrane, then endocytosed to early and recycling endosomes; this itinerary is tightly regulated and affects amyloidogenic processing. (pqac-00000012) | (pqac-00000012) |
| Subcellular localization | Major functional compartments | Major APP β-cleavage by neuronal BACE1 is linked to early endosomes; increased APP-BACE1 colocalization in early endosomes correlates with higher sAPPβ/Aβ production in human iPSC-derived neurons. (pqac-00000005, pqac-00000012) | (pqac-00000005, pqac-00000012) |
| Subcellular localization | Endolysosomal system | BACE1 is also reported in late endosomes and lysosomes, consistent with its acidic pH requirement and with roles in APP processing and Aβ34 generation. (pqac-00000008, pqac-00000011) | (pqac-00000008, pqac-00000011) |
| Trafficking regulation | Sorting machinery | Post-Golgi export of BACE1 depends on AP-1 and Arf1/Arf4, and altered trafficking increases APP cleavage and Aβ40/Aβ42 production. (pqac-00000012) | (pqac-00000012) |
| Post-translational modifications | Functional importance of PTMs | PTMs are essential for maturation, trafficking, stability, and enzymatic competence of BACE1; reviews specifically highlight glycosylation, phosphorylation, palmitoylation, and acetylation. (pqac-00000001) | (pqac-00000001) |
| Post-translational modifications | Glycosylation | Glycosylation is described as required for proper maturation/trafficking and contributes to APP-cleaving function. (pqac-00000001) | (pqac-00000001) |
| Post-translational modifications | Phosphorylation | Phosphorylation is implicated in BACE1 trafficking and amyloidogenic processing; BACE1 phosphorylation at Ser498 is discussed in relation to APP amyloidogenic processing. (pqac-00000001, pqac-00000006) | (pqac-00000001, pqac-00000006) |
| Post-translational modifications | Palmitoylation | Palmitoylation is listed among core PTMs that regulate BACE1 maturation and intracellular trafficking. (pqac-00000001) | (pqac-00000001) |
| Post-translational modifications | Acetylation | Acetylation is also reviewed as a BACE1 PTM relevant to post-translational control of the protein. (pqac-00000001) | (pqac-00000001) |


*Table: This table summarizes core biochemical and cell-biological properties of human BACE1, including its domain structure, catalytic features, intracellular sites of action, trafficking, and key post-translational modifications. It is useful as a compact reference for functional annotation of BACE1.*