Regulation of amyloid beta-peptide levels by enzymatic degradation.

It is generally accepted that amyloid beta peptides (Abeta) play a significant role in the etiology of Alzheimer's disease. The Abeta peptides are produced by the sequential cleavage of an amyloid precursor protein by a betasecretase followed by cleavage by a gamma secretase. The clearance of beta appears to be due primarily by the action of one or more peptidases. An imbalance between the rate of synthesis and the rate of clearance of Abeta is now considered a possible contributor to the onset of Alzheimer's disease. This review focuses on peptidases that have been proposed to contribute to Abeta catabolism and discusses the evidence for their participation in Abeta peptide clearance in vivo.