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p3 peptide also known as amyloid β- peptide (Aβ) 17–40/42 is the peptide resulting from the α-and γ-secretase cleavage from the amyloid precursor protein ().It is known to be the major constituent of diffuse plaques observed in Alzheimer's disease (AD) brains and pre-amyloid plaques in people affected by Down syndrome.
Amyloid is formed through the polymerization of hundreds to thousands of monomeric peptides or proteins into long fibers. Amyloid formation involves a lag phase (also called nucleation phase), an exponential phase (also called growth phase) and a plateau phase (also called saturation phase), as shown in the figure.
Amyloid beta (Aβ, Abeta or beta-amyloid) denotes peptides of 36–43 amino acids that are the main component of the amyloid plaques found in the brains of people with Alzheimer's disease. [2] The peptides derive from the amyloid-beta precursor protein (APP), which is cleaved by beta secretase and gamma secretase to yield Aβ in a cholesterol ...
The normal function of Aβ is not certain, but plaques arise when the protein misfolds and begins to accumulate in the brain by a process of molecular templating ('seeding'). [36] Mathias Jucker and Lary Walker have likened this process to the formation and spread of prions in diseases known as spongiform encephalopathies or prion diseases.
Amyloid-beta precursor protein (APP) is an integral membrane protein expressed in many tissues and concentrated in the synapses of neurons. It functions as a cell surface receptor [5] and has been implicated as a regulator of synapse formation, [6] neural plasticity, [7] antimicrobial activity, [8] and iron export. [9]
Thus, alpha-secretase cleavage precludes amyloid beta formation and is considered to be part of the non-amyloidogenic pathway in APP processing. Alpha secretases are members of the ADAM ('a disintegrin and metalloprotease domain') family, which are expressed on the surfaces of cells and anchored in the cell membrane .
Amyloid light chains deposition in shoulder joint causes enlarged shoulders, also known as "shoulder pad sign". [18] Amyloid light chain depositions can also cause bilateral symmetric polyarthritis. [18] The deposition of amyloid proteins in the bone marrow without causing plasma cell dyscrasias is called amyloidoma. It is commonly found in ...
Amyloid beta (Aβ) is composed of a family of peptides produced by proteolytic cleavage of the type I transmembrane spanning glycoprotein amyloid-beta precursor protein (APP). Amyloid plaque Aβ protein species ends in residue 40 or 42, [ 4 ] but it is suspected that Aβ42 form is crucial in the pathogenesis of AD.