Comparative studies on peptides representing the so-called tachykinin-like region of the Alzheimer Aβ peptide [Aβ(25-35)]

In an attempt to answer the question of whether or not the so-called tachykinin-like region of the Alzheimer beta-amyloid protein [A beta(25-35)] can act as a tachykinin, the sequences A beta(25-35), A beta(25-35)amide and their norleucine-35 and phenylalanine-31 analogues were synthesized. These peptides were examined with ligand binding studies, electron microscopy, CD and NMR, In all cases some differences were found between the A beta(25-35) analogue and the corresponding Phe(31) peptide. In addition: in ligand displacement studies on tachykinin NK1 receptors, only the Phe31 analogue showed activity comparable to that of genuine tachykinins, We conclude that peptides based on A beta(25-35) but with a Phe residue at position 31 do display properties typical of a tachykinin, but that peptides with Ile at this position do not.