Evaluation of superior BACE1 cleavage sequences containing unnatural amino acids.

A recombinant form of BACE1 (β-site amyloid precursor protein cleaving enzyme-1) corresponding to positions 46-454 of the extracellular domain of the original membrane enzyme was prepared. The recombinant BACE1 (rBACE1) had the kinetic parameters K(m)=5.5μM and k(cat)=1719s(-1). Using several libraries of substrates containing unnatural amino acids, the specificity of rBACE1 was evaluated. LC/MS of digests derived from the libraries clarified that a dodecapeptide containing unnatural amino acids at P(2) to [Formula: see text] was a superior cleavage sequence.