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Lysozymes
Lysozyme (, muramidase, ''N''-acetylmuramide glycanhydrolase; systematic name peptidoglycan ''N''-acetylmuramoylhydrolase) is an antimicrobial enzyme produced by animals that forms part of the innate immune system. It is a glycoside hydrolase that catalyzes the following process: : Hydrolysis of (1→4)-β-linkages between ''N''-acetylmuramic acid and ''N''-acetyl-D-glucosamine residues in a peptidoglycan and between ''N''-acetyl-D-glucosamine residues in chitodextrins Peptidoglycan is the major component of gram-positive bacterial cell wall. This hydrolysis in turn compromises the integrity of bacterial cell walls causing lysis of the bacteria. Lysozyme is abundant in secretions including tears, saliva, human milk, and mucus. It is also present in cytoplasmic granules of the macrophages and the polymorphonuclear neutrophils (PMNs). Large amounts of lysozyme can be found in egg white. C-type lysozymes are closely related to α-lactalbumin in sequence and structure, making t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycoside Hydrolase Family 22
In molecular biology, glycoside hydrolase family 22 is a family of glycoside hydrolases. , which are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycoside hydrolases, based on sequence similarity, has led to the definition of >100 different families. This classification is available on the CAZy web site, and also discussed at CAZypedia, an online encyclopedia of carbohydrate active enzymes. Glycoside hydrolase family 2CAZY GH_22comprises lysozyme type C () lysozyme type i () and alpha-lactalbumins. Asp and/or the carbonyl oxygen of the C-2 acetamido group of the substrate acts as the catalytic nucleophile/base. Alpha-lactalbumin, is a milk protein that acts as the regulatory subunit of lactose synthetase, acting to promote the conversion of galactosyltransferase to lactose synthase, which is essential for milk production. In the mammary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saliva
Saliva (commonly referred as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (such as lingual lipase and amylase), and antimicrobial agents (such as secretory IgA, and lysozymes). The enzymes found in saliva are essential in beginning the process of digestion of dietary starches and fats. These enzymes also play a role in breaking down food particles entrapped within dental crevices, thus protecting teeth from bacterial decay. Saliva also performs a lubricating function, wetting food and permitting the initiation of swallowing, and protecting the oral mucosa from drying out. Saliva has specialized purposes for a variety of animal species beyond predigestion. Certain swifts construct nests with their sticky saliva. The foundation of bird's nest soup is an aerodramus nest. Venom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melting Point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilibrium, equilibrium. The melting point of a substance depends on pressure and is usually specified at a Standard temperature and pressure, standard pressure such as 1 Atmosphere (unit), atmosphere or 100 Pascal (unit), kPa. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of substances to Supercooling, supercool, the freezing point can easily appear to be below its actual value. When the "characteristic freezing point" of a substance is determined, in fact, the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice, that is, the #Melting point measurements, melting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxocarbenium
In organic chemistry, an oxocarbenium ion (alternatively spelled oxacarbenium) is a chemical species characterized by a central sp2-hybridized atom of carbon, a substituent atom of oxygen, and an overall positive charge that is delocalized between the central carbon and oxygen atoms (). An oxocarbenium ion is represented by two limiting resonance structures, one in the form of a carbenium ion with the positive charge on carbon () and the other in the form of an oxonium species with the formal charge on oxygen (). As a resonance hybrid, the true structure falls between the two. Compared to neutral carbonyl () compounds like ketones () or esters, the carbenium ion form is a larger contributor to the structure. They are common reactive intermediates in the hydrolysis of glycosidic bonds, and are a commonly used strategy for chemical glycosylation. These ions have since been proposed as reactive intermediates in a wide range of chemical transformations, and have been utilized in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbohydrate
A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' may differ). This formula does not imply direct covalent bonding between hydrogen and oxygen atoms; for example, in , hydrogen is covalently bonded to carbon, not oxygen. While the 2:1 hydrogen-to-oxygen ratio is characteristic of many carbohydrates, exceptions exist. For instance, uronic acids and deoxy-sugars like fucose deviate from this precise stoichiometric definition. Conversely, some compounds conforming to this definition, such as formaldehyde and acetic acid, are not classified as carbohydrates. The term is predominantly used in biochemistry, functioning as a synonym for saccharide (), a group that includes sugars, starch, and cellulose. The saccharides are divided into four chemical groups: monosaccharides, disaccharides, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
N-Acetylmuramic Acid
''N''-Acetylmuramic acid (NAM or MurNAc) is an organic compound with the chemical formula . It is a monomer of peptidoglycan in most bacterial cell walls, which is built from alternating units of ''N''-acetylglucosamine (GlcNAc) and ''N''-acetylmuramic acid, cross-linked by oligopeptides at the lactic acid residue of MurNAc. Formation of NAM NAM is an addition product of phosphoenolpyruvate and ''N''-acetylglucosamine. This addition happens exclusively in the cell cytoplasm. Clinical significance ''N''-Acetylmuramic acid (MurNAc) is part of the peptidoglycan polymer of bacterial cell walls. MurNAc is covalently linked to ''N''-acetylglucosamine and may also be linked through the hydroxyl on carbon number 4 to the carbon of L-alanine. A pentapeptide composed of L-alanyl-D-isoglutaminyl-L-lysyl-D-alanyl-D-alanine is added to the MurNAc in the process of making the peptidoglycan strands of the cell wall. Synthesis of NAM is inhibited by fosfomycin. NAG and NAM cross-linking ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substrate (chemistry)
In chemistry, the term substrate is highly context-dependent. Broadly speaking, it can refer either to a chemical species being observed in a chemical reaction, or to a surface on which other chemical reactions or microscopy are performed. In the former sense, a reagent is added to the ''substrate'' to generate a product through a chemical reaction. The term is used in a similar sense in synthetic and organic chemistry, where the substrate is the chemical of interest that is being modified. In biochemistry, an enzyme substrate is the material upon which an enzyme acts. When referring to Le Chatelier's principle, the substrate is the reagent whose concentration is changed. ;Spontaneous reaction : :*Where S is substrate and P is product. ;Catalysed reaction : :*Where S is substrate, P is product and C is catalyst. In the latter sense, it may refer to a surface on which other chemical reactions are performed or play a supporting role in a variety of spectroscopic and micr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gram-positive Bacteria
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. The Gram stain is used by microbiologists to place bacteria into two main categories, gram-positive (+) and gram-negative (−). Gram-positive bacteria have a thick layer of peptidoglycan within the cell wall, and gram-negative bacteria have a thin layer of peptidoglycan. Gram-positive bacteria retain the crystal violet stain used in the test, resulting in a purple color when observed through an optical microscope. The thick layer of peptidoglycan in the bacterial cell wall retains the stain after it has been fixed in place by iodine. During the decolorization step, the decolorizer removes crystal violet from all other cells. Conversely, gram-negative bacteria cannot retain the violet stain after the decolorization step; alcohol used in this stage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chitinase
Chitinases (, chitodextrinase, 1,4-β-poly-N-acetylglucosaminidase, poly-β-glucosaminidase, β-1,4-poly-N-acetyl glucosamidinase, poly[1,4-(N-acetyl-β-D-glucosaminide)] glycanohydrolase, (1→4)-2-acetamido-2-deoxy-β-D-glucan glycanohydrolase; systematic name (1→4)-2-acetamido-2-deoxy-β-D-glucan glycanohydrolase) are hydrolytic enzymes that break down glycosidic bonds in chitin. They catalyse the following reaction: : Random endo-hydrolysis of ''N''-acetyl-β-D-glucosaminide (1→4)-β-linkages in chitin and chitodextrins As chitin is a component of the cell walls of fungi and exoskeleton, exoskeletal elements of some animals (including mollusks and arthropods), chitinases are generally found in organisms that either need to reshape their own chitin or dissolve and digest the chitin of fungi or animals. Species distribution Chitinivorous organisms include many bacteria (Aeromonadales, Aeromonads, ''Bacillus'', ''Vibrio'', among others), which may be pathogenic or det ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chitin
Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chitin are produced each year in the biosphere. It is a primary component of cell walls in fungi (especially filamentous and mushroom-forming fungi), the exoskeletons of arthropods such as crustaceans and insects, the radulae, cephalopod beaks and Gladius (cephalopod), gladii of molluscs and in some nematodes and diatoms. It is also synthesised by at least some fish and lissamphibians. Commercially, chitin is extracted from the shells of crabs, shrimps, shellfish and lobsters, which are major by-products of the seafood industry. The structure of chitin is comparable to cellulose, forming crystalline nanofibrils or whiskers. It is functionally comparable to the protein keratin. Chitin has proved useful ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
