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 ...
derived from D-
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usi ...
, linked by
glycosidic bond
A glycosidic bond or glycosidic linkage is a type of covalent 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 gr ...
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 termed the "penicillin of antifungals," along ...
class.
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 covalent 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 gr ...
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, 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. The polysaccharide structure represents the main storage form of glucose in the body.
Glycogen functions as one o ...
, α-1,4- and α-1,6-glucan
*
pullulan, 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 diets ...
, 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 20–30%. Because of its tightly packed helical structure, amylose ...
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 amyl ...
, both α-1,4- and α-1,6-glucans
Beta
*
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
, 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 us ...
, 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 '' A ...
, 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 diato ...
, β-1,3- and β-1,6-glucan
*
lentinan, a strictly purified β-1,6:β-1,3-glucan from ''
Lentinus edodes''
*
lichenin, β-1,3- and β-1,4-glucan
*
oat beta-glucan
Oat β-glucans are water-soluble β-glucans derived from the endosperm of oat kernels known for their dietary contribution as components of soluble fiber. Due to their property to lower serum total cholesterol and low-density lipoprotein cholest ...
, β-1,3- and β-1,4-glucan
*
pleuran, β-1,3- and β-1,6-glucan isolated from ''
Pleurotus ostreatus
''Pleurotus ostreatus'', the oyster mushroom, oyster fungus, or hiratake, is a common edible mushroom. It was first cultivated in Germany as a subsistence measure during World War I and is now grown commercially around the world for food. It is ...
''
*
zymosan
Zymosan is a glucan with repeating glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during phot ...
, 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 ...
s derived from
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usi ...
monomers. The monomers are linked by
glycosidic bonds
A glycosidic bond or glycosidic linkage is a type of covalent 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 gr ...
. 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 diets ...
), 1,4- (
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
), 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 diato ...
), 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 resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional ...
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= -CH
3,
[ -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 held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
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
In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
Classification
...
to the 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
Carbohydrate chemistry is a subdiscipline of chemistry primarily concerned with the detection, synthesis, structure, and function of carbohydrates. Due to the general structure of carbohydrates, their synthesis is often preoccupied with the selec ...
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.
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. The polysaccharide structure represents the main storage form of glucose in the body.
Glycogen functions as one o ...
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 diets ...
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.
See also
* Glucanase
Glucanases are enzymes that break down large polysaccharides via hydrolysis. The product of the hydrolysis reaction is called a glucan, a linear polysaccharide made of up to 1200 glucose monomers, held together with glycosidic bonds. Glucans are a ...
References
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Polysaccharides