Glucan 1,4-a-glucosidase
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A glucan is a
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wat ...
derived from D-
glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
, linked by
glycosidic bond A glycosidic bond or glycosidic linkage is a type of ether bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group o ...
s. Glucans are noted in two forms: alpha glucans and beta glucans. Many
beta-glucan Beta-glucans, β-glucans comprise a group of β-D-glucose polysaccharides ( glucans) naturally occurring in the cell walls of cereals, bacteria, and fungi, with significantly differing physicochemical properties dependent on source. Typically, ...
s are medically important. They represent a drug target for antifungal medications of the
echinocandin Echinocandins are a class of antifungal drugs that inhibit the synthesis of β-glucan in the fungal cell wall via noncompetitive inhibition of the enzyme 1,3-β glucan synthase. The class has been dubbed the "penicillin of antifungals," along w ...
class. In the field of bacteriology, the term polyglucan is used to describe high molecular mass glucans. They are structural polysaccharide consisting of a long linear chain of several hundred to many thousands
D-glucose Glucose is a sugar with the molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae during photosynthesis from water and ...
monomers. The point of attachment is O-glycosidic bonds, where a
glycosidic A glycosidic bond or glycosidic linkage is a type of ether bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group of a ...
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
links the glycoside to the reducing end sugar. Polyglucans naturally occur in the cell walls of bacteria. Bacteria produce this polysaccharide in a cluster near the bacteria's cells. Polyglucan's are a source of beta-glucans. Structurally, beta 1.3-glucans are complex glucose homopolymers binding together in a beta-1,3 configuration.


Types

The following are glucans (The α- and β- and numbers clarify the type of O-
glycosidic bond A glycosidic bond or glycosidic linkage is a type of ether bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group o ...
and the specific carbons involved):


Alpha

*
dextran Dextran is a complex branched glucan (polysaccharide derived from the condensation of glucose), originally derived from wine. IUPAC defines dextrans as "Branched poly-α-d-glucosides of microbial origin having glycosidic bonds predominantly C-1 ...
, α-1,6-glucan with α-1,3-branches *
floridean starch Floridean starch is a type of storage glucan found in glaucophytes and in red algae (or rhodophytes), in which it is usually the primary sink for fixed carbon from photosynthesis. It is found in grains or granules in the cell's cytoplasm and is c ...
, α-1,4- and α-1,6-glucan *
glycogen Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. It is the main storage form of glucose in the human body. Glycogen functions as one of three regularly used forms ...
, α-1,4- and α-1,6-glucan *
pullulan Pullulan is a polysaccharide consisting of maltotriose units, also known as α-1,4- ;α-1,6-glucan'. Three glucose units in maltotriose are connected by an α-1,4 glycosidic bond, whereas consecutive maltotriose units are connected to each other ...
, α-1,4- and α-1,6-glucan *
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...
, a mixture of
amylose Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch, making up approximately 20–25% of it. Because of its tightly packed Helix, helical struct ...
and
amylopectin Amylopectin is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose. Plants store starch within specialized organelles called amyloplas ...
, both α-1,4- and α-1,6-glucans * α-1,2-glucan, α-1,2-glucan


Beta

*
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...
, β-1,4-glucan *
chrysolaminarin Chrysolaminarin is a linear polymer of β(1→3) and β(1→6) linked glucose units in a ratio of 11:1. It used to be known as leucosin. Function Chrysolaminarin is a storage polysaccharide typically found in photosynthetic heterokonts. It is u ...
, β-1,3-glucan *
curdlan Curdlan is a water-insoluble linear beta-1,3-glucan, a high-molecular-weight polymer of glucose. Curdlan consists of β-(1,3)-linked glucose residues and forms elastic gels upon heating in aqueous suspension. It was reported to be produced by '' ...
, β-1,3-glucan *
laminarin The molecule laminarin (also known as laminaran) is a storage glucan (a polysaccharide of glucose) found in brown algae. It is used as a carbohydrate food reserve in the same way that chrysolaminarin is used by phytoplankton, especially in diat ...
, β-1,3- and β-1,6-glucan *
lentinan Lentinan is a polysaccharide isolated from the fruit body of shiitake mushroom (''Lentinula edodes''). Chemistry Lentinan is a β-1,3 beta-glucan with β-1,6 branching. It has a molecular weight of 500,000 Da and specific rotation of +14-22° (N ...
, a strictly purified β-1,6:β-1,3-glucan from ''
Lentinus edodes The shiitake (; ''Chinese/black mushroom'' or ''Lentinula edodes'') is a macrofungus native to East Asia, which is cultivated and consumed around the globe. Taxonomy The fungus was first described scientifically as ''Agaricus edodes'' by M ...
'' *
lichenin Lichenin, also known as lichenan or moss starch, is a complex glucan occurring in certain species of lichens. It can be extracted from ''Cetraria islandica'' ( Iceland moss). It has been studied since about 1957. Structure Chemically, lichenin ...
, β-1,3- and β-1,4-glucan *
oat beta-glucan Oat β-glucans are water-soluble Beta-glucan, β-glucans derived from the endosperm of oat kernels known for their dietary contribution as components of dietary fiber, soluble fiber. Due to their property to lower serum total cholesterol and low-d ...
, β-1,3- and β-1,4-glucan *
pleuran Pleuran is an insoluble polysaccharide ( β-(1,3/1,6)-D-glucan), isolated from ''Pleurotus ostreatus''. Pleuran belongs to a group of glucose polymers commonly called beta-glucans demonstrating biological response modifier properties. These immu ...
, β-1,3- and β-1,6-glucan isolated from ''
Pleurotus ostreatus ''Pleurotus ostreatus'' (commonly known the oyster mushroom, grey oyster mushroom, oyster fungus, hiratake, or pearl oyster mushroom). Found in temperate and subtropical forests around the world, it is a popular edible mushroom. Name Both th ...
'' *
zymosan Zymosan is a beta-glucan with repeating glucose units connected by β-1,3-glycosidic linkages. It binds to TLR 2 and Dectin-1 ( CLEC7A). Zymosan is a ligand found on the surface of fungi, like yeast. Zymosan is prepared from yeast cell walls a ...
, β-1,3-glucan


Properties

Properties of glucans include resistance to oral acids/enzyme and water insolubility. Glucans extracted from grains tend to be both soluble and insoluble.


Structure

Glucans are
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wat ...
s derived from
glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
monomers. The monomers are linked by
glycosidic bonds A glycosidic bond or glycosidic linkage is a type of ether bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group of ...
. Four types of glucose-based polysaccharides are possible: 1,6- (
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...
), 1,4- (
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...
), 1,3- (
laminarin The molecule laminarin (also known as laminaran) is a storage glucan (a polysaccharide of glucose) found in brown algae. It is used as a carbohydrate food reserve in the same way that chrysolaminarin is used by phytoplankton, especially in diat ...
), and 1,2-bonded glucans. The first representatives of main chain unhydrolysable linear polymers made up of
levoglucosan Levoglucosan (C6H10O5) is an organic compound with a six-carbon ring structure formed from the pyrolysis of carbohydrates, such as starch and cellulose. As a result, levoglucosan is often used as a chemical tracer for biomass burning in atmospheri ...
units were synthesized in 1985 by anionic polymerization of 2,3-
epoxy Epoxy is the family of basic components or Curing (chemistry), cured end products of epoxy Resin, resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide fun ...
derivatives of levoglucosan (1,6;2,3-dianhydro-4-O-alkyl-β-D-mannopyranoses).Berman, E.L., Gorkovenko A.A., Zubov, V.P., and Ponomarenko, V.A., "Regio and Stereospecific Synthesis of Polyglucose with Novel Type Bond" Soviet J.Bioorg. Chem. 11 (1985), 1125-1129 A wide range of unique monomers with different radical R can be synthesized. There were synthesized polymers with R= -CH3, -CH2CHCH2, and -CH2C6H5.Gorkovenko, A.A., Berman, E.L., and Ponomarenko, V.A. "A New Polymer of Glucose. Poly(2 3) D glucose" Soviet J. Bioorg. Chem., 1987, 13, 218 222 Investigation of the polymerization kinetics of those derivatives,
molecular weight A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...
and molecular-weight distribution showed that the polymerization has the features of a living polymerization system. The process takes place without termination and transfer of the polymer chain with a degree of polymerization equal to the mole ratio of the
monomer A monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or two- or three-dimensional network in a process called polymerization. Classification Chemis ...
to the
initiator An initiator can refer to: * A person who instigates something. * Modulated neutron initiator, a neutron source used in some nuclear weapons ** Initiator, an Explosive booster ** Initiator, the first Nuclear chain reaction * Pyrotechnic initiator, ...
. Accordingly, the upper value molecular weight polymer determines only degree of purification system what determine the presence in the system uncontrollable amount of terminators of polymer chains. Poly(2-3)-D-glucose was synthesized proceeds by transformation of benzyl (R= -CH2C6H5) functionalized polymer. Polymerization of 3,4-epoxy levoglucosan (1,6;3,4-dianhydro-2-O-alkyl-β-D-galactopyranose) results in formation 3,4-bounded levoglucosan polymer. The presence of 1,6-anhydro structure in every unit of polymer chains allows researchers to apply all spectra of well developed methods of
carbohydrate chemistry 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'' ma ...
with formation of highly intriguing biological application polymers. The polymers are the only known regular polyethers built up of carbohydrate units in main polymer chain.


Biochemical synthesis

Photosynthetic Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...
microorganisms A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...
, such as
cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
and
microalgae Microalgae or microphytes are microscopic scale, microscopic algae invisible to the naked eye. They are phytoplankton typically found in freshwater and marine life, marine systems, living in both the water column and sediment. They are unicellul ...
, are currently used for their polyglucan production. Since these organisms have high-photosynthetic activity and whole-year cultivation without utilization of arable land. The cultivation is done by modifying the nutrient supply and replacing the growth medium of the cyanobacteria and green microalgae since the control and manipulation of polyglucan metabolism necessitates the elucidation of the polyglucan production mechanism. These activities promote the growth of polyglucans from these organisms. Several cyanobacteria enzymes could synthesis α-1,2-glucan.


Functions

Glucans serve a diverse set of functions. Within the cell, certain glucans store energy, fortify cellular structure, behave in recognition, and enhance virulence in pathogenic organisms.
Glycogen Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. It is the main storage form of glucose in the human body. Glycogen functions as one of three regularly used forms ...
and
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...
are notable glucans responsible for storing energy for the cell. Receptor molecules of the immune system, such as the Complement receptor 3, or CR3, and CD5 receptor, recognize and bind to beta-glucans on invading cell surfaces. Polyglucans are utilized as a
carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
source for microbial
fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...
. Although polyglucan production has so far been promoted by nutrient limitation, it must be further enhanced to accommodate market demand. The combined strategies of cultivation design and
genetic engineering Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of Genetic engineering techniques, technologies used to change the genet ...
are used for polyglucan productivity for
bioethanol Ethanol fuel is fuel containing ethyl alcohol, the same type of alcohol as found in alcoholic beverages. It is most often used as a motor fuel, mainly as a biofuel additive for gasoline. Several common ethanol fuel mixtures are in use a ...
production. Polyglucans are also involved in another sector of the energy industry, acting as
biopolymers Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, ...
to increase oil recovery. The polysaccharide is attached to the bacteria cells and then mixed in an
alkali In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The a ...
solution such as
sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly corrosive base (chemistry), ...
to become
soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...
. After which, it is then pumped into the injection well. The reason it needs to be a fluid is so you can pump the polysaccharides into the reservoir, but then the polysaccharide needs to gel/solidify/precipitate
in situ is a Latin phrase meaning 'in place' or 'on site', derived from ' ('in') and ' ( ablative of ''situs'', ). The term typically refers to the examination or occurrence of a process within its original context, without relocation. The term is use ...
upon addition of another chemical in order to plug up the pore. The biopolymer is then combined and injected with water until it fills up at least 30% of the empty pores. Next, there is an injection of an acid solution or forming . This neutralizes the solution and allows for the precipitation of the biopolymer, polyglucans, inside the high-permeability zones. Evidence shows that the application of this polyglucan can reduce the permeability of approximately 80% of the high-permeability zones. Oil companies are able to benefit from the decreased permeability because oil tends to flow in areas with the highest permeability. They can also serve as dietary supplements.


Clinical significance

The immune-modulation action of polyglucans has been known for over 40 years, after experiments showed that they stimulated the activation of
macrophages Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...
through the activation of the complement system. The detection of the (1,3)-β-D-glucan in blood is also used as a means of identifying invasive or disseminated fungal infections. Although, a positive test does not render a diagnosis, and a negative test does not rule out infection. This test can aid in the detection of
Aspergillus ' () is a genus consisting of several hundred mold species found in various climates worldwide. ''Aspergillus'' was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microscope, Miche ...
, Candida, and Pneumocystis jirovecii.


See also

*
Glucanase Glucanases are enzymes that break down lucanspolysaccharides via hydrolysis. The product of the hydrolysis reaction are smaller glucans, a linear or branched polysaccharide made of up to 1200 glucose monomers, linked by glycosidic bonds. Glucans a ...


References

{{Authority control Polysaccharides