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Pepsin
Pepsin is an endopeptidase that breaks down proteins into smaller peptides and amino acids. It is one of the main digestive enzymes in the digestive systems of humans and many other animals, where it helps digest the proteins in food. Pepsin is an aspartic protease, using a catalytic aspartate in its active site. It is one of three principal endopeptidases (enzymes cutting proteins in the middle) in the human digestive system, the other two being chymotrypsin and trypsin. There are also exopeptidases which remove individual amino acids at both ends of proteins (carboxypeptidases produced by the pancreas and aminopeptidases secreted by the small intestine). During the process of digestion, these enzymes, each of which is specialized in severing links between particular types of amino acids, collaborate to break down dietary proteins into their components, i.e., peptides and amino acids, which can be readily absorbed by the small intestine. The cleavage specificity o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aspartic Protease
Aspartic proteases (also "aspartyl proteases", "aspartic endopeptidases") are a catalytic type of protease enzymes that use an activated water molecule bound to one or more aspartate residues for catalysis of their peptide substrates. In general, they have two highly conserved aspartates in the active site and are optimally active at acidic pH. Nearly all known aspartyl proteases are inhibited by pepstatin. Aspartic endopeptidases of vertebrate, fungal and retroviral origin have been characterised. More recently, aspartic endopeptidases associated with the Prepilin peptidase, processing of bacterial type 4 prepilin and archaean preflagellin have been described. Eukaryotic aspartic proteases include pepsins, cathepsins, and renins. They have a two-domain structure, arising from ancestral duplication. HIV-1 protease, Retroviral and retrotransposon proteases (retroviral aspartyl proteases) are much smaller and appear to be homologous to a single domain of the eukaryotic aspartyl pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastric Chief Cell
A gastric chief cell, peptic cell, or gastric zymogenic cell is a type of gastric gland cell that releases pepsinogen and gastric lipase. It is the cell responsible for secretion of chymosin (rennin) in ruminant animals and some other animals. The cell stains basophilic upon H&E staining due to the large proportion of rough endoplasmic reticulum in its cytoplasm. Gastric chief cells are generally located deep in the mucosal layer of the stomach lining, in the fundus and body of the stomach. Chief cells release the zymogen (enzyme precursor) pepsinogen when stimulated by a variety of factors including cholinergic activity from the vagus nerve and acidic condition in the stomach. Gastrin and secretin may also act as secretagogues. It works in conjunction with the parietal cell, which releases gastric acid, converting the pepsinogen into pepsin. Nomenclature The terms ''chief cell'' and '' zymogenic cell'' are often used without the word "gastric" to name this type of cell. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digestion
Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream. Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. Mechanical digestion takes place in the mouth through Chewing, mastication and in the small intestine through segmentation contractions. In chemical digestion, enzymes break down food into the small compounds that the body can use. In the human digestive system, food enters the mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastric Acid
Gastric acid or stomach acid is the acidic component – hydrochloric acid – of gastric juice, produced by parietal cells in the gastric glands of the stomach lining. In humans, the pH is between one and three, much lower than most other animals, but is very similar to that of carrion-eating carnivores that need protection from ingesting pathogens. With this higher acidity, gastric acid plays a key protective role against pathogens. It is also key in the digestion of proteins by activating digestive enzymes, which together break down the long chains of amino acids. Gastric acid is regulated in feedback systems to increase production when needed, such as after a meal. Other cells in the stomach produce bicarbonate, a base, to buffer the fluid, ensuring a regulated pH. These cells also produce mucus – a viscous barrier to prevent gastric acid from damaging the stomach. The pancreas further produces large amounts of bicarbonate, secreting this through the pancreatic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zymogen
In biochemistry, a zymogen (), also called a proenzyme (), is an inactive precursor of an enzyme. A zymogen requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) to become an active enzyme. The biochemical change usually occurs in Golgi bodies, where a specific part of the precursor enzyme is cleaved in order to activate it. The inactivating piece which is cleaved off can be a peptide unit, or can be independently-folding domains comprising more than 100 residues. Although they limit the enzyme's ability, these N-terminal extensions of the enzyme or a "prosegment" often aid in the stabilization and folding of the enzyme they inhibit. The pancreas secretes zymogens partly to prevent the enzymes from digesting proteins in the cells where they are synthesised. Enzymes like pepsin are created in the form of pepsinogen, an inactive zymogen. Pepsinogen is activated when chief cells release ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pepstatin
Pepstatin is a potent inhibitor of aspartyl proteases. It is a hexa-peptide containing the unusual amino acid statine (Sta, (3S,4S)-4-amino-3-hydroxy-6-methylheptanoic acid), having the sequence Isovaleryl-Val-Val-Sta-Ala-Sta (Iva-Val-Val-Sta-Ala-Sta). It was originally isolated from cultures of various species of Actinomyces due to its ability to inhibit pepsin at picomolar concentrations. It was later found to inhibit nearly all acid proteases with high potency and, as such, has become a valuable research tool, as well as a common constituent of protease inhibitor cocktails. Pepstatin A is well known to be an inhibitor of aspartic proteases such as pepsin, cathepsins D and E. Except for its role as a protease inhibitor, however, the pharmacological action of pepstatin A upon cells remain unclear. Pepstatin A suppresses receptor activator of NF-κB ligand (RANKL)–induced osteoclast differentiation. Pepstatin A suppresses the formation of multinuclear osteoclasts dose-dependen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theodor Schwann
Theodor Schwann (; 7 December 181011 January 1882) was a German physician and physiology, physiologist. His most significant contribution to biology is considered to be the extension of cell theory to animals. Other contributions include the discovery of Schwann cells in the peripheral nervous system, the discovery and study of pepsin, the discovery of the Organism, organic nature of yeast, and the invention of the term "metabolism". Early life and education Theodor Schwann was born in Neuss on 7 December 1810 to Leonard Schwann and Elisabeth Rottels. Leonard Schwann was a goldsmith and later a printer. Theodor Schwann studied at the Dreikönigsgymnasium (also known as the Tricoronatum or Three Kings School), a Jesuit school in Cologne. Schwann was a devout Roman Catholic. In Cologne his religious instructor , a priest and novelist, emphasized the individuality of the human soul and the importance of free will. In 1829, Schwann enrolled at the University of Bonn in the preme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrochloric Acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is a component of the gastric acid in the digestive systems of most animal species, including humans. Hydrochloric acid is an important laboratory reagent and industrial chemical. Etymology Because it was produced from halite, rock salt according to the methods of Johann Rudolph Glauber, hydrochloric acid was historically called by European alchemists ''spirits of salt'' or ''acidum salis'' (salt acid). Both names are still used, especially in other languages, such as , , , , , , , , , , (''ensan''), zh, 盐酸 (''yánsuān''), and (''yeomsan''). Gaseous HCl was called ''marine acid air''. The name ''muriatic acid'' has the same origin (''muriatic'' means "pertaining to brine or salt", hence ''muriate'' means hydrochloride), and this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Howard Northrop
John Howard Northrop (July 5, 1891 – May 27, 1987) was an American biochemist who, with James Batcheller Sumner and Wendell Meredith Stanley, won the 1946 Nobel Prize in Chemistry. The award was given for these scientists' isolation, crystallization, and study of enzymes, proteins, and viruses. Northrop was a Professor of Bacteriology and Medical Physics, Emeritus, at University of California, Berkeley. Biography Early years Northrop was born in Yonkers, New York to John Isaiah, a zoologist and instructor at Columbia University who is a member of the Havemeyer family, and Alice Rich Northrop, a teacher of botany at Hunter College. His father died in a lab explosion two weeks before John H. Northrop was born. The son was educated at Yonkers High School and Columbia University, where he earned his BA in 1912 and PhD in chemistry in 1915. During World War I, he conducted research for the U.S. Chemical Warfare Service on the production of acetone and ethanol through ferm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digestive Enzyme
Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes in the mouth, stomach, pancreas, and duodenum, before being able to be absorbed into the bloodstream. Initial breakdown is achieved by chewing (mastication) and the use of digestive enzymes of saliva. Once in the stomach further mechanical churning takes place mixing the food with secreted gastric acid. Digestive gastric enzymes take part in some of the chemical process needed for absorption. Most of the enzymatic activity, and hence absorption takes place in the duodenum. Digestive enzymes are found in the digestive tracts of animals (including humans) and in the tracts of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular surv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amino Acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 appear in the genetic code of life. Amino acids can be classified according to the locations of the core structural functional groups ( alpha- , beta- , gamma- amino acids, etc.); other categories relate to polarity, ionization, and side-chain group type ( aliphatic, acyclic, aromatic, polar, etc.). In the form of proteins, amino-acid '' residues'' form the second-largest component (water being the largest) of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis. It is thought that they played a key role in enabling life on Earth and its emergence. Amino acids are formally named by the IUPAC- IUBMB Joint Commi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
