PolysaccharideGlycosidic bondCombinedsugar chainAt least more than 10 monosaccharides are composed of polymeric sugars, high molecular carbohydrates.By the samemonosaccharideThe composition of polysaccharide is calledHomopolysaccharide, such asstarch、celluloseandGlycogen；Polysaccharides composed of different monosaccharides are calledHeteropolysaccharide, such asGum arabicIs created byPentoseandGalactoseEtc.Polysaccharide is not a pure chemical substance, but a mixture of substances with different degrees of polymerization.Polysaccharides are generally insoluble in water, have no sweet taste, cannot form crystals, and have no reducibility andTrochanter phenomenon。Polysaccharides are also glycosides, so they can be hydrolyzed. In the process of hydrolysis, a series of intermediate products are often produced, and finallyhydrolysisGet monosaccharides.[1]
Chinese name
Polysaccharide
Foreign name
polysaccharide
chemical formula
(CsixHtenOfive)n
Water solubility
Generally insoluble in water[1]
Substantive
Glycoside bonded sugar chain[1]
Classification
Isopolysaccharide, heteropolysaccharide[1]
Sweet taste
No sweet taste[1]
Hydrolysis
It can be hydrolyzed and the final product is monosaccharide[1]
Polysaccharide is composed ofmonosaccharideFormed by molecular condensation and dehydration, it is a kind of carbohydrate with complex and huge molecular structure.WherePolymer compoundConceptualcarbohydrateAnd its derivatives are called polysaccharides.Polysaccharides are widely distributed and important in nature.Some are the components that make up the cell walls of animals and plants, such asPeptidoglycanandcellulose；Some are nutrients stored as animals and plants, such asGlycogenandstarch；Some have specialbiological activity, like in human bodyheparinThe polysaccharide in the cell wall of pneumococcus has antigenic effect.[2]
Encyclopedia x confusion: diagram of monosaccharide and polysaccharide
PolysaccharideStructural unitIt is a monosaccharide, and the relative molecular weight of polysaccharide ranges from tens of thousands to tens of millions.The structural units are connected by glycosidic bonds. The common glycosidic bonds are α - 1,4-glycosidic bonds, β - 1,4-glycosidic bonds and α - 1,6-glycosidic bonds.The structural units can be linked into linear chains or branched chains. The linear chains are generally linked by α - 1,4-glycosidic bonds (such as starch) and β - 1,4-glycosidic bonds (such as cellulose);The connection point between chains in the branched chain is usually α - 1,6-glycosidic bond.[3]
Consisting of one type of monosaccharideglucose、Mannan、GalactanConsisting of more than two monosaccharidesHeteropolysaccharideThere are gum arabic and so on, which are diverse in chemical structure.In terms of molecular weight, there are from 5000 molecules to more than 106 polysaccharides.Short chains less than 10 are calledoligosaccharide。However, as far as the sugar chain is concerned, even oligosaccharides, which combine protein and lipid on oligosaccharides, as far as the whole molecule is concerned, if they belong to polymers, they also belong to polysaccharides in a broad sense, so they are specially calledComplex polysaccharideOr compound sugar.[4]
Polysaccharide, also known as glycan, refers to the polymer compounds formed by a large number of monosaccharides (glycose) through glycosidic bonds.Polysaccharides formed from the same monosaccharide fragments are called homopolysaccharides or homoglycans;Polysaccharides composed of two or more different monosaccharides can be called heteropolysaccharides or heteroglycans.[10]
(1) The same name as polysaccharide: use "D -" or "L -" to indicate the configuration of sugar;If the connection mode of the polysaccharide is the same, the glycoside bond is marked in front of the configuration symbol with numbers and arrows;If the connection mode is different, the connection mode may not be marked.[10]
(2) Name of heteropolysaccharide: when heteropolysaccharide has a main chain (skeleton) composed of only one sugar residue, this sugar residue placed at the end is called glycan, and the other residues are prefixed in alphabetical order according to the English prefix.When there is no single sugar type main chain, all residues are arranged in alphabetical order according to the English prefix, and end with the suffix "glycan".[10]
classification
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Polysaccharides can be broadly classified into homogeneous polysaccharides and heterogeneous polysaccharides.[5]
Homogeneous polysaccharide
By amonosaccharidePolysaccharides condensed from molecules are called homogeneous polysaccharides.The most abundant homogeneous polysaccharides in nature are starch, glycogen and cellulose.They are all made of glucose.Starch and glycogen are the storage forms of glucose in plants and animals respectively, and cellulose is the main structural component of plant cells.[5]
1. Starch
Starch is a storage form of plant nutrients and an important nutrient component in plant foods. It is divided intoAmyloseandamylopectin。[5]
①AmyloseMany α - glucose are glucose polymers that grow in sequence with α - 1,4-glycosidic bonds without separation.It is typically composed of thousands of glucose ligands, with molecular weights ranging from 150000 to 600000.The structure is long and compact spiral tube.This compact structure is compatible with its storage function.Blue in case of iodine.[5]
②amylopectin: An α - 1,6 branched chain is formed every 20-25 glucose residues on the basis of the straight chain.Spiral tube can not be formed, and it will be purple in case of iodine.[5]
2. Glycogen
GlycogenSimilar to amylopectin, but with a higher degree of branching, there is one branch every four glucose residues.The more compact structure is more suitable for its storage function, which is an important reason for animals to use it as a form of energy storage. Another reason is that it contains a large number of non original ends, which can be quickly mobilized for hydrolysis.Glycogen is reddish brown when it meets iodine.[5]
3. Cellulose structure
Many β - D-glucose molecules are linked by β - (1-4) glycosidic bonds to form straight chains.Cellulose is the main structural component of plant cell wall, accounting for about 1/3 of the total weight of plants. It is also the most abundant organic matter in nature. About 1011 tons of cellulose are produced annually on the earth.Wood, paper, fiber, cotton, linen.The intact cell wall is mainly composed of cellulose and adhered withhemicellulose、pectinandLignin。About 40 cellulose chainshydrogen bondConnected with fibroblast filaments, countless filaments form a complete fiber skeleton of cell wall.Cellulose that degrades cellulose mainly exists in microorganisms. Some ruminants can use microorganisms in their digestive tract to digest cellulose, and produce glucose for their own use and common use by microorganisms.Although most animals (including humans) cannot digest cellulose, food containing cellulose is necessary and beneficial to health.[5]
4. Chitin
N-acetyl-D-glucosamine to (1,4)GlycosideA straight chain connected by chains.[5]
5. Inulin
Polyfructose, found in the roots of compositae plants.[5]
6. Agar
Polygalactose is a polysaccharide contained in some seaweeds. People and microorganisms cannot digest agar.[5]
Heterogeneous polysaccharide
Polysaccharide condensed from different monosaccharide molecules is called heterogeneous polysaccharide.Common ones are:Hyaluronic acid、chondroitin sulfateEtc.[5]
Some heterogeneous polysaccharides are composed of repeat glycosaminoglycansdisaccharideSeries composition, calledGlycosaminoglycan, also known as mucopolysaccharide, amino polysaccharide, etc.[5]
Glycosaminoglycans are the main components of proteoglycans. According to the different repeat disaccharide units, there are five types of glycosaminoglycans:
Polysaccharides have no sweet taste and can only form real solution in watercolloid, the relative molecular weight is very high, so there is no reducibility, no tropy, but there isoptical rotation。[1]
biological function
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Some polysaccharides, such as cellulose and chitin, can form plant or animal skeletons.Polysaccharides such as starch and glycogen can be used as energy storage materials for organisms.Heterogeneous polysaccharide passes throughcovalent bondComposed of proteinProteoglycanGive play to biological functions, such as as body lubricant, cells for identifying foreign tissues, basic components of blood group substances, etc.[5]
Plant polysaccharides can be increased bymacrophageVolume to improve immunity.The effect of plant polysaccharide on phagocytosis of macrophages is related to its concentration, and it can promote phagocytosis of macrophages within an appropriate concentration range.Plant polysaccharides can regulate macrophagescell factorTo regulate the function of macrophages.Plant polysaccharides can affect the function of macrophages by regulating the activity of enzymes in macrophages.[6]
Plant polysaccharide pairlymphocyteThe regulatory effect of TNF - α is mainly reflected in its proliferation ability, subgroup structure, cytokine secretion, etc.A certain concentration of plant polysaccharides can promote the proliferation of lymphocytes, improve the structure of lymphocyte subsets, and thus regulate the immune function of the body.Plant polysaccharides can enhance the immune function of the body by promoting the secretion of cytokines.Plant polysaccharide can improve the antibody level in animal serum and enhance the immune function.[6]
Plant polysaccharides can activateNatural killer cellsAnd enhance its killing activity.[6]
Angelica polysaccharide, Poria cocos polysaccharide, Hydrangea cone polysaccharide, jujube seed polysaccharide, etc. can be activatedComplement system。[6]
Anti virus and anti-cancer
Polysaccharides have cytotoxic effect on tumor cells and play a direct anti-tumor role.Some polysaccharides can induce apoptosis and inhibit differentiation of tumor cells.The capsular polysaccharide extracted from Escherichia coli can inhibit the metastasis of B16-BL16 melanoma cells and MDA-MB-231 breast cancer cells, and can reduce the adhesion of B16-BL16 to endothelial cells, intercellular adhesion molecules, and selective proteins.[7]
Some polysaccharides have no direct inhibitory effect on tumor cells, but play an anti-tumor role by enhancing the immune function of the body. The immune regulation of polysaccharides is one of the main mechanisms of anti-tumor effect.[7]
Polysaccharides play an anti-tumor role mainly through the following ways: direct cytotoxicity, immune enhancement, and synergistic effect with traditional anti-tumor drugs.The direct anti-tumor effect of polysaccharide is to inhibit the growth of tumor cells by inducing apoptosis of cancer cells, blocking cell cycle, and inhibiting invasion, adhesion and metastasis of tumor cells;The indirect anti-tumor effect of polysaccharide is to enhance the immune function of the host through the immune enhancement effect.[7]
Hypoglycemic
Mushroom traditional Chinese medicine polysaccharide has good hypoglycemic and antidiabetic effects. It mainly affects glucose metabolism by promoting liver glycogen synthesis, promoting glycolysis or inhibiting the activity of α - glucosidase, and can also directly act on pancreatic islet beta cells, promote insulin secretion and increase insulin secretionInsulin sensitivityAnd enhance antioxidant stress to play a hypoglycemic function.Therefore, the hypoglycemic mechanism of fungus Chinese medicine polysaccharide is characterized by multiple effects, multiple targets and multiple pathways.[8]
Other uses
Polysaccharides have large molecular weight and usually exist in the form of main chain and side chain. This structure determines that they have processing properties and rheological properties that other substances do not have.At the same time, it has a polyhydroxy structure and spatial folding, which will have good hydrophilicity and certain emulsifying ability. It is easy to form gel in water and has a high viscosity.Adding polysaccharide to the beverage can increase the viscosity and stability of the beverage, and also give the beverage a fresh taste;In flour products processing, polysaccharide can enhance gluten water holding capacity and improve gluten elasticity;Adding a certain amount of polysaccharide to meat products can also effectively improve the water holding capacity of meat products and improve the texture of meat products (such as elasticity, slicing, etc.).At the same time, polysaccharide also has many functions such as anti-aging, anti-oxidation, anti ulcer, and regulating the body immunity.[9]
