The proteins BACE1 and BACE2 and beta-secretase activity in normal and Alzheimer's disease brain.Biochem Soc Trans. 2007 Jun; 35(Pt 3):574-6.BS
The insidious progression of AD (Alzheimer's disease) is believed to be linked closely to the production, accumulation and aggregation of the approximately 4.5 kDa protein fragment called Abeta (amyloid beta-peptide). Abeta is produced by sequential cleavage of the amyloid precursor protein by two enzymes referred to as beta- and gamma-secretase. beta-Secretase is of central importance, as it catalyses the rate-limiting step in the production of Abeta and was identified 7 years ago as BACE1 (beta-site APP-cleaving enzyme 1). Soon afterwards, its homologue BACE2 was discovered, and both proteins represent a new subclass of the aspartyl protease family. Studies examining the regulation and function of beta-secretase in the normal and AD brain are central to the understanding of excessive production of Abeta in AD, and in targeting and normalizing this beta-secretase process if it has gone awry in the disease. Several reports indicate this, showing increased beta-secretase activity in AD, with recent findings by our group showing changes in beta-secretase enzyme kinetics in AD brain caused by an increased V(max). This article gives a brief review of studies which have examined BACE1 protein levels and beta-secretase activity in control and AD brain, considering further the expression of BACE2 in the human brain.