Enzyme Shreds Alzheimer's Protein

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Alzheimer's Protein and Enzyme

An enzyme found naturally in the brain snips apart the protein that forms the sludge called amyloid plaque that is one of the hallmarks of Alzheimer's disease (AD), researchers have found. They said their findings in mice suggest that the protein, called Cathepsin B (CatB), is a key part of a protective mechanism that may fail in some forms of Alzheimer's disease. Also, they said their findings suggest that drugs to enhance CatB activity could break down amyloid deposits, counteracting one of the central pathologies of Alzheimer's disease.

Li Gan and colleagues published their findings in the September 21, 2006, issue of the journal Neuron, published by Cell Press.

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Their experiments were prompted by previous studies showing that the cysteine protease CatB - an enzyme that snips apart proteins - closely associated with the amyloid-ъ (Aъ) protein that forms the amyloid plaques, a hallmark of AD. However, those studies had not determined whether CatB was "good" or "bad"--that is, whether it acted to produce Aъ from a longer protein, called amyloid precursor protein (APP), or whether it broke down Aъ.

In their experiments, Gan and colleagues determined that CatB was the latter--breaking down Aъ, apparently to enable other enzymes to further degrade the protein for the cell's protein "garbage deposal" system.

They found that knocking out the CatB gene increased plaque deposition in a mouse model of

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