Irvine Gb

Expression and activity of β-site amyloid precursor protein cleaving enzyme in Alzheimer's disease

Several lines of evidence indicate that the Aβ peptide is involved at some level in the pathological process that results in the clinical symptoms of AD (Alzheimer9s disease). The N-terminus of Aβ is generated by cleavage of the Met-Asp bond at position 671–672 of APP (amyloid precursor protein), catalysed by a proteolytic activity called β-secretase. Two ‘β-secretase’ proteases have been identified: BACE (β-site APP-cleaving enzyme) and BACE2. The cause of sporadic AD is currently unknown, but some studies have reported elevated BACE/β-secretase activity in brain regions affected by the disease. We have demonstrated that robust β-secretase activity is also detectable in platelets that contain APP and release Aβ. This review considers the current evidence for alterations in β-secretase activity, and/or alterations in BACE expression, in post-mortem brain tissue and platelets from individuals with AD.

Aminopeptidase activities present in tissues of Helix aspersa

1. Tissues of Helix aspersa have been examined for the presence of aminopeptidase activities. 2. Enzyme activities were detected using synthetic peptide substrates containing the fluorescent leaving group 7-amino-4-methyl coumarin. The methods used included continuous fluorimetric assay and activity staining of enzymes in non-denaturing polyacrylamide gels. 3. Several types of peptidase activity were detected, including three distinct aminopeptidases which differ in molecular size and substrate preference.