Amyloid Peptides

Amyloid beta (Aβ or Abeta) refers to peptides of 36–43 amino acids that are a major component of the amyloid plaques found in the brains of Alzheimer disease patients.

Aβ is formed from cleavage of amyloid precursor protein (APP) by β- and γ-secretases. Cleavage by γ-secretase is not precise and consequently C-terminal heterogeneity of the resulting peptide population means that multiple Aβ species exist, but those ending at position 40 (Aβ40) are the most abundant (up to 90%), followed by those ending at position 42 (Aβ42, up to 10%).

Although Aβ40 is the most common, Aβ42 is more fibrillogenic and thus more associated with disease states. The two hallmark pathologies of Alzheimer’s disease (AD) are the extracellular plaque deposits of Aβ and neurofibrillary tangles of the microtubule binding protein tau. Aβ proteins have also been associated with other diseases such as Lewy body dementia, inclusion body myositis and cerebral amyloid angiopathy.