CHOLINESTERASE ACTIVITY IN THE PLAQUES, TANGLES AND ANGIOPATHY OF ALZHEIMERS-DISEASE DOES NOT EMANATE FROM AMYLOID

Previous histochemical observations in our laboratory have demonstrate d the presence of butyrylcholinesterase and an enzymatically altered f orm of acetylcholinesterase activity in the plaques, tangles and amylo id-containing vessels of Alzheimer's disease. These findings suggested possible interactions between amyloid and cholinesterases. In this st udy we employed a cholinesterase biochemical assay to determine whethe r the amyloid precursor protein either had cholinesterase activity its elf or influenced the enzymatic activity of cholinesterases. None of t he three amyloid precursor sequences used (695, 751, 770, up to 16 mu g/ml) exhibited any acetylcholinesterase or butyrylcholinesterase acti vity that could be detected by our method. In addition, none of the am yloid precursor proteins influenced the enzymatic activity of purified acetylcholinesterase or butyrylcholinesterase in a specific manner. I t is therefore quite unlikely that amyloid can, by itself, account for the intense cholinesterase activity associated with the pathological lesions of AD.