Amyloid-beta precursor protein secretase
Type of enzyme From Wikipedia, the free encyclopedia
Type of enzyme From Wikipedia, the free encyclopedia
Secretases are enzymes that "snip" pieces off a longer protein that is embedded in the cell membrane.
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Among other roles in the cell, secretases act on the amyloid-beta precursor protein (APP) to cleave the protein into three fragments.[citation needed] Sequential cleavage by beta-secretase 1 (BACE) and gamma-secretase (γ-secretase) produces the amyloid-beta peptide fragment that aggregates into clumps called amyloid plaques in the brains affected by Alzheimer's disease.[1] If alpha-secretase (α-secretase) acts on APP first instead of BACE, no amyloid beta is formed because α-secretase recognizes a target protein sequence closer to the cell surface than BACE. The non-pathogenic middle fragment formed by an α/γ cleavage sequence is called P3.[citation needed]
The structure of the three secretases varies widely.
Besides their involvement in the pathogenesis of Alzheimer's, these proteins also have other functional roles in the cell.
γ-secretase plays a critical role in developmental signalling by the transmembrane receptor Notch, freeing the cytoplasmic tail of Notch to travel to the cell nucleus to act as a transcription factor.
Although BACE cleaves the extracellular domains of several transmembrane proteins, its physiological function remains unknown.
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