Secretases are enzymes that "snip" pieces off a longer protein that is embedded in the cell membrane. Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = blend) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... The cell membrane (also called the plasma membrane, plasmalemma or phospholipid bilayer) is a semipermeable lipid bilayer common to all living cells. ...

Processing of the amyloid precursor protein

Among other roles in the cell, secretases act on the amyloid precursor protein (APP) to cleave the protein into three fragments. Sequential cleavage by β-secretase (BACE) and γ-secretase produces the amyloid-β peptide fragment that aggregates into clumps called "plaques" in the brains of Alzheimer's disease patients. If α-secretase acts on APP first instead of BACE, no amyloid-β 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. Image File history File links Download high-resolution version (1199x899, 55 KB) Depiction of amyloid precursor protein processing, created by I. Peltan Ipeltan I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high-resolution version (1199x899, 55 KB) Depiction of amyloid precursor protein processing, created by I. Peltan Ipeltan I, the creator of this work, hereby release it into the public domain. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... The metal-binding domain of APP with a bound copper ion. ... β-secretase — also called BACE1 (β-site of APP cleaving enzyme) or memapsin-2 — is an aspartic-acid protease important in the pathogenesis of Alzheimers disease. ... Gamma secretase is a multi-subunit protease complex, itself an integral membrane protein, that cleaves single-pass transmembrane proteins at residues within the transmembrane domain. ... Amyloid beta (Aβ or Abeta) is a peptide of 39-43 amino acids that is the main constituent of amyloid plaques in the brains of Alzheimers disease patients. ... sBold text == Headline text ==please edit this page!!!!! omething Gisela does not have These where evolved into our heads. ... Peptide sequence or amino acid sequence is the order in which amino acid residues, connected by peptide bonds, lie in the chain. ...

The structure of the three secretases varies widely. The α-secretase gene has not been conclusively identified but is believed to be a metalloproteinase. BACE is a transmembrane protein with an extracellular aspartic acid protease domain. γ-secretase is actually a protein complex containing presenilin, nicastrin, ACH-1, and PEN-2. Presenilin is believed to harbor the protease domain and represents an important example of a rare type of protease that cleaves targets within the cell membrane. Proteins are an important class of biological macromolecules present in all biological organisms, made up of such elements as carbon, hydrogen, nitrogen, oxygen and sulfur. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... The metalloendopeptidases (also called metalloproteinases or metalloproteases) are a class of enzymes from the group of endopeptidases. ... Aspartic acid Aspartic acid proteases are protease enzymes which have an aspartic acid residue in the active site of the enzyme. ... In biology, a domain (also superregnum, superkingdom, or empire) is the top-level grouping of organisms in scientific classification, higher than a kingdom. ... A protein complex is a group of two or more associated proteins formed by protein-protein interaction that is stable over time. ... Presenilins are a family of related multi-pass transmembrane proteins that function as a part of the gamma-secretase protease complex. ... Proteases (proteinases, peptidases, or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. ...

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. Overview of signal transduction pathways In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in... Transmembrane receptors are integral membrane proteins, which reside and operate typically within a cells plasma membrane, but also in the membranes of some subcellular compartments and organelles. ... The Notch pathway is a gene regulatory pathway involved in multiple differentiation processes. ... Cytoplasm is the viscid, semi-fluid matter contained within the plasma membrane of a cell that helps to hold the cell together. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. ...