β-secretase — also called BACE1 (β-site of APP cleaving enzyme) or memapsin-2 — is an aspartic-acid protease important in the pathogenesis of Alzheimer's disease. The transmembrane protein, contains two active site aspartate residues in its extracellular Protein domain and may function as a dimer. Proteases (proteinases, peptidases or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. ... Pathogenesis is the mechanism by which a certain etiological factor causes disease (pathos = disease, genesis = development). ... NIGGGGGGGGAAAAAAAAAAAAAAAA PLEASE A transmembrane protein is an integral membrane protein that spans from the internal to the external surface of the biological membrane or lipid bilayer in which it is embedded. ... Aspartic acid, also known as aspartate, the name of its anion, is one of the 20 natural proteinogenic amino acids which are the building blocks of proteins. ... In cell biology, molecular biology and related fields, the word extracellular means outside the cell. It is used in contrast to intracellular (inside the cell). ... Within a protein, a structural domain (domain) is an element of overall structure that is self-stabilizing and often folds independently of the rest of the protein chain. ... Sucrose, or common table sugar, is composed of glucose and fructose. ...

Processing of the amyloid precursor protein

Generation of the 40 or 42 amino acid-long amyloid-β peptides that aggregate in the brain of Alzheimer's patients requires two sequential cleavages of the amyloid precursor protein (APP). Extracellular cleavage of APP by BACE releases a soluble extracellular fragment and is followed by APP cleavage within its transmembrane domain by γ-secretase. The second cleavage releases the intracellular domain of APP and amyloid-β. Since α-secretase cleaves APP closer to the cell membrane than BACE does, it removes a fragment of the amyloid-β peptide. Initial cleavage of APP by α-secretase rather than BACE prevents eventual generation of amyloid-β. An amino acid residue is what is left of an amino acid once a molecule of water has been lost (an H+ from the nitrogenous side and an OH- from the carboxylic side) in the formation of a peptide bond. ... Amyloid beta (Aβ or Abeta) is a protein fragment of 39-42 amino acids that is the main constituent of amyloid plaques in various neurological disorders, most prominently Alzheimers disease. ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... Amyloid beta (Aβ or Abeta) is a protein fragment on 39-42 amino acids that is the main constituent of amyloid plaques in various neurological disorders, most prominently Alzheimers disease. ... Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ...

Unlike APP and the presenilin proteins important in γ-secretase, no known mutations in the gene encoding BACE cause the early-onset, familial Alzheimer's disease. However, levels of this enzyme have been shown to be elevated in Alzheimer's. The physiological purpose of BACE's cleavage of APP and other transmembrane proteins is unknown. BACE2 is a close homolog of BACE1. This article is about mutation in biology, for other meanings see: mutation (disambiguation). ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... In biology, two or more structures are said to be homologous if they are alike because of shared ancestry. ...

Drugs to block this enzyme (BACE inhibitors) in theory would prevent the build up of beta-amyloid and may help slow or stop the disease. Several companies are in the early stages of development and testing of this new potential class of treatment (Walker and Rosen 2006).

References

• OMIM 604252
• LF Walker, RC Rosen. "Alzheimer therapeutics—what after the cholinesterase inhibitors?" Age and Ageing 2006 35(4): 332-335. PMID 16644763