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Amyloid beta peptide (beta-APP)
Abeta 2lfm.jpg
A partially folded structure of amyloid beta(1 40) in an aqueous environment (pdb 2lfm)
Identifiers
Symbol APP
Pfam PF03494
InterPro IPR013803
SCOP 2lfm
SUPERFAMILY 2lfm
TCDB 1.C.50
OPM superfamily 369
OPM protein 2y3k
amyloid beta (A4) precursor protein (peptidase nexin-II, Alzheimer disease)
APP processing.png
Processing of the amyloid precursor protein
Identifiers
Symbol APP
Alt. symbols AD1
Entrez 351
HUGO 620
OMIM 104760
RefSeq NM_000484
UniProt P05067
Other data
Locus Chr. 21 q21.2

Amyloid beta ( or Abeta) denotes peptides of 36–43 amino acids that are crucially involved in Alzheimer's disease as the main component of the amyloid plaques found in the brains of Alzheimer patients. The peptides result from the amyloid precursor protein (APP), which is cleaved by beta secretase and gamma secretase to yield Aβ. Aβ molecules can aggregate to form flexible soluble oligomers which may exist in several forms. It is now believed that certain misfolded oligomers (known as "seeds") can induce other Aβ molecules to also take the misfolded oligomeric form, leading to a chain reaction akin to a prion infection. The seeds or the resulting amyloid plaques are toxic to nerve cells. The other protein implicated in Alzheimer's disease, tau protein, also forms such prion-like misfolded oligomers, and there is some evidence that misfolded Aβ can induce tau to misfold.

A recent study suggested that APP and its amyloid potential is of ancient origins, dating as far back as early deuterostomes.

The normal function of Aβ is not well understood. Though some animal studies have shown that the absence of Aβ does not lead to any loss of physiological function, several potential activities have been discovered for Aβ, including activation of kinase enzymes, protection against oxidative stress, regulation of cholesterol transport, functioning as a transcription factor, and anti-microbial activity (potentially associated with Aβ's pro-inflammatory activity).

Per a study published in the 2016 May 25 issue of Science Translational Medicine, Amyloid-beta protein may fight other diseases, attacking pathogens in mice and worms.

The glymphatic system clears metabolic waste from the mammalian brain, and in particular beta amyloids. The rate of removal is significantly increased during sleep. However the significance of the glymphatic system is unknown in clearance of Aβ.


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