Glycolipids, belonging to lipid compounds, are widely found in variousorganismMedium.Glycolipids in nature can be divided into two categories according to the types of alcohol groups in their components:Glycerol glycolipidandGlycosphingolipid。GlycosylationGlycerol glycolipids, known as glycerol glycolipids, are found in nerve tissues of animals, plants and microorganisms. They are the main glycolipids in plants, as well as some bacteria, especiallyGram positive bacteriaCommon components of bacterial membrane[1]。
Chinese name
Glycolipids
Foreign name
glycolipid(s)[6]
Classification
Glycerol glycolipids and glycosphingolipids
Features
It is widely distributed, but its content is small
Glycolipids are lipid compounds containing glycosyl ligands.It is a kind of amphiphilic molecule, which exists widely in organisms.
"Glycolipids" refers to any one of the following group of compounds: the compound contains one or more monosaccharide residues, its glycosidic bond and a hydrophobic part such asAcylglycerol、Sphingosine(a long-chain aliphatic amino alcohol)ceramide（N-Acylsphingosine) or isoprene phosphate."Glycerol glycolipids" are glycolipids containing one or more glycerol residues."Glycosphingolipids" are lipids containing at least one monosaccharide residue and one sphingosine or ceramide.[6]
Glycolipids can be divided into four categories according to the different lipid parts:
(3) Glycolipids derived from phosphate terpenoid alcohols;
(4) Steroid derived glycolipids[2]。
Glycerol glycolipid
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structure
Glycidylglycerid: Glycidylglycerol is similar to phospholipid in structure. The main chain is glycerol, containing fatty acids, but not containing phosphorus, choline and other compounds.Sugar residues are formed byGlycosidic bondConnected at 1, 2-DiacylglycerolC-3 ofGlycosyl glycerideMolecules.It is known that this kind of glycolipids can be composed of various sugarsPolar head。There are not only diacyl oil esters, but also 1-acyl congeners.
The sugars in natural glycolipid molecules mainly include glucoseGalactose, most fatty acids areUnsaturated fatty acid。Named according to the International Committee on Biochemical Names:GalactosylDiacylglycerol and dihemiLactose groupThe structure of diacylglycerol is 1,2-diacyl-3-O-β-D-PyranGalactosyl-glycerolAnd 1,2-diacyl-3-O-（α-D-galactopyranosyl (1 → 6) - O-β-D galactopyranosyl) - glycerol.
In addition, there are trigalactosylDiacylglycerol, 6-O-acyl monogalactosyl diacylglycerol, etc.
Glycerol glycolipid compounds isolated in nature can be roughly divided into the following categories:
(1) Ester linked glycerol glycolipid;
(2) The hydroxyl group of the glycerol part of the ether glyceride glycolipid is alkylated to form an ether bond instead of an ester bond;
(3) Glycerol glycolipid with fatty acylation of hydroxyl group on sugar group;
(4) Glucuronic glyceryl glycolipids;
(5) Glycerol glycolipids aminated at sugar sites;
(6) Glycerol glycolipid sulfonated at position 6 of sugar group;
(7) Glycerol glycolipid in which both hydroxyl groups of glycerol are glycosylated.
The experiment found that the glycerol glycolipid M874B can also protecttwoOtwoThe cell death caused by HtwoOtwoReleasedHydroxyl radical, which indicates that MGDG (such as M874B) is a new typeOxygen free radical scavenger, which can remove some active oxygen molecules.M874B is capable of scavenging hydroxyl radicals andhydrogen peroxideThe activity of free radicals is related to theGalactosylStructure related, increase or decrease one galactose group, even ifacylDifferent, they will lose their activity.
(2) Inhibition of enzyme
Since the 1980s, it has been found that thioisorhamose diacylglycerol (SQDG) isolated from different organisms can strongly inhibit mammalsDNA Polymeraseα，DNA PolymeraseβAnd terminal deoxynucleotidyltransferase (TdT) activity, moderately inhibiting humanImmunodeficiency virus HIV-RT activity of reverse transcriptase, and these inhibitory effects are dose dependent;The inhibitory effect is also related to the chain length of fatty acids and the sulfonic groups on SQDG.However, sulfolipids do not inhibit prokaryotesDNA Polymerase[1]。
(3) Antiviral
Reshef et al. isolated 26 glycolipid compounds from five cyanobacteria, including 11 SQDG, 6 DGDG and 9 MGDG.These compounds can inhibit the activity of HIV-l reverse transcriptase to varying degrees. Four glycolipids that can effectively inhibit the activity of HIV-1 and HIV-2 reverse transcriptase are SQDG, and the final concentration is 10μAt mol/L, the reverse transcriptase DNA polymerase activity is almost 100% inhibited, but the RNA enzyme (RnaSeH) inhibitory activity is very low or not.Subsequently, Loya et al. further studied the structure-activity relationship of the four sulfurized glycolipids that can effectively inhibit HIV reverse transcriptase activity.It was found that if the 2, 3 hydroxyl groups on the sugar ring were replaced by palmitoyl residues, the ability of the compound to inhibit reverse transcriptase activity was significantly reduced, possibly because the acyl group in the molecule hindered the inhibition through steric hindrance.Sulfonic acid group andfatty acidThe side chain plays a decisive role in its antiviral ability. When the sulfonic acid group is removed, the inhibitory effect of the four tested natural sulfuretted glycolipids will be weakened, and the hydrolysis of the side chain fatty acid will lose most of its inhibition of HIV RT activity. It is speculated that the hydrophobic core reaction between the lipophilic group and the enzyme, and the negatively charged sulfonic acid part interacts with the enzyme's positively charged side chain[1]。
Some glycerol glycolipids, including MGDG and DGDG, were isolated from two toxic marine dinoflagellates, and they all have hemolytic activity.Nine dinoflagellates collected from the ocean depths of subtropical waters were found to have high lethality, fish toxicity and hemolysis to mice. Among them, the hemolytic substances isolated from the former Cattlefish were MGDG and DGDG[1]。
The glycosphingolipids containing multiple sugar groups can be divided into two categories: nonesialic acidNeutral glycosphingolipids and acidic glycosphingolipids containing sialic acid.Due to the increasing number of glycosphingolipids that clarify the structure, and based on the composition and structure of several kernel sugar groups close to ceramide, glycosphingolipids are further divided into four series: globo series, muco series, lacto series, and ganglio series (Table 1).Each series is also divided into several small groups.
effect
also calledGlycosphingolipid。The parent structure of glycosphingolipids isceramide。Fatty acids are linked to the C-2 amino group of long-chain sphingosine, and the ceramide saccharides formed are hydrophilic to glycosphingolipidsPolar head。Sugar containing one or more neutral sugar residues as polar headSphingolipidsIt is called neutral glycosphingolipids orGlycosylCeramide, whose polar head is charged, is the simplestCerebrosideIt's in GodhydroxylUp, withβGlycosideConnect a sugar group (glucose orGalactose）。
Important sugarSphingolipidsThere are cerebrosides andGanglioside。Brain glycosides are the most abundant in brain, followed by lung and kidney, liver, spleen and serum.The cerebroside in the brain is mainly galactoside, and its fatty acid is mainly twenty-four carbon fatty acid;The blood is mainly composed of glucose, cerebroside, gangliosidesialic acidAcid glycosphingolipids.Sialic acid is also calledN-acetylneuraminic acidIt passes throughα-Glycosidic bondIt is linked to glycolipids.Ganglioside molecules are composed of galactose (Gal), N-acetylgalactose (GalNAc), glucose (Glc), N-fatty sphingosine (Cer), and sialic acid (NeuAc).Gangliosides are widely distributed on the outer surface of cell membranes in various tissues of the body, with brain tissue being the most abundant.
GlycosphingolipidThe blood type determines the function.red blood cellplasma membraneThe sugar sphingolipids on theABO blood group systemBlood group antigenImmunological activityThe molecular basis of specificity issugar chainOfGlycosylform.A. The sugar chain structures of B and O blood group antigens are basically the same, but the sugar groups at the end of the sugar chain are different.The sugar chain end of type A blood is N-acetylGalactose；Type B bloodIs galactose;Both AB type sugar groups are present,Type O bloodThese two sugar groups are missing.
Glycolipids are one of the components of cell membrane and play an important role in cell adhesion, growth, differentiation, signal transduction, etcCell recognition, immune inhibition and other important physiological processes.[3]
Other glycolipids
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Glycolipid linkage
GlycosylAcylglycerolOne of the sugar group and glycerolhydroxylwithGlycosidic bondThe other two hydroxyl groups of glycerol are connected with a fatty acid respectively;These glycolipids are found in animal and plant tissues.A very small amount of sterol glycosides was also found in plants.Bacteria, exceptmacromoleculelipopolysaccharideIn addition, glycolipids of various structures are often produced.Including: Glycerol, the lipid formed by sugar and fatty acid, whose sugar base is mostlyD-mannoseandD-glucose；Glycolipids - and commonGlycerol phosphateLipids are mixed together, but sugar groups replace the positions of bases and alcohols;And esters formed by sugar and fatty acid, containingphenolFormed by terminal hydroxyl hydrocarbonGlycosidewait.
MycobacterialCapsuleA poisonous glycolipid is separated from the trehalose and branched fatty acid diester.It can promoteMycobacteriumIt is connected into a long cord like chain, called cord factor.There are also some long-chain fatty acids orAlkyl groupGlycosides of derivatives, whichGlycosylParts are oftenDisaccharideorTrisaccharide, containing some rare monosaccharides.
Glucuronic acid glycolipid
Nitrogen, phosphorus and potassium are three essential elements for plant growth. Lack of phosphorus will lead to short plants and plump fruits.Japanese scientists found that a kind of glycolipid in plants can enable them to maintain growth in a phosphorus deficient environment, and determined the gene that guides the synthesis of this glycolipid.This will help scientists cultivate crops that can tolerate phosphorus deficiency.
The Japanese Institute of Physics and Chemistry and the Agency for the Promotion of Science and Technology jointly issued a press release a few days ago, saying that plant biofilms are mainly composed of phospholipids and glycolipids. When plants lack phosphorus, phospholipids in the biofilms will decrease. At the same time, some glycolipids will increase to make up for the lack of phospholipids, so as to maintain the biofilms and help plants grow normally.This phenomenon is called recombination of membrane lipids, which plays an important role in the survival of plants in phosphorus deficient environment.However, it has not been clear exactly which compounds participate in membrane lipid recombination.
The team of the Plant Science Research Center of the Institute of Physics and Chemistry, with the help of the comprehensive analysis method of intracellular low molecular metabolites developed independently, analyzed theArabidopsis thalianaThe membrane lipids in the body were recombined, and aGlucuronic acidGlycolipids are accumulated in the aboveground part of Arabidopsis plants.This glycolipid has only been found in some microbiota before.
The researchers also cultivated Arabidopsis thaliana with some gene defects related to glycolipid synthesis in plants. They found that if Arabidopsis did not have the SQD2 gene, glucuronic acid glycolipid could not be accumulated, and it would wither earlier than normal Arabidopsis plants under phosphorus deficiency.
The bulletin said that phosphate rock is an important raw material for the production of chemical fertilizers, which is showing signs of depletion and is becoming a major concern in the agricultural field.Based on this discovery, scientists are expected to cultivate crops that are tolerant to phosphorus deficiency.
Relevant papers have been published in the new British online scientific journal Nature Communications.
distribution
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SphingolipidsIs dynamicplant cellAn important component of the membrane, in the brain andNervous tissueIt is very high in fat storage, but very low in fat storage.GlycosphingolipidDistribution inMembranous lipidIn the outer layer of double layer, nonPolarityThe hydrocarbon long chain of is buried outsideLipid layerMedium, polarsugar chainIt extends into the extracellular aqueous phase.useOrganic solventorDetergentIt can extract glycosphingolipids from the membrane.In addition, there is a very small amount of glycolipids in cells, which are intermediate carriers in the process of sugar chain synthesis.
Macroporous adsorption resin method is mainly used for rough separation of samples. The obtained product is a mixture of glucose and lipid, and it is difficult to obtain a single compound.For example, Cao Dongxu[4]Using carp surimi as the raw material of sugar and fat, 90% ethanol extract was separated with HP-20 macroporous adsorption resin, and 90% ethanol andchloroformElution: the 90% ethanol eluate obtained is separated with HP-20 macroporous adsorption resin, eluted with 70% ethanol and 95% ethanol in turn, and the 95% ethanol eluate is collected and concentrated, which is the glycolipid concentrated substance.
High performance thin layer chromatography
Murakami et al. use the fresh leaves of Thai herbal medicine lime as raw materials to obtainethyl acetateExtraction phase, proceedDextran gelC-100 column chromatography, the eluent is acetone/toluene solution with successively increased acetone concentration, and 60-80% acetone eluate is obtained.Then, carry outInverted silica gelColumn chromatography, methanol/water (9:1, v/, r) and methanol/acetonitrile/water (16:4:5, v/v~) were used as eluents to obtain the mixture containing glycerol glycolipid DLGG and LPG, and then high performance thin layer chromatography was used to prepare silica gel plate for separation to obtain glycerol glycolipid monomer DLGG and LPG.EfficientThin layer chromatographyIn order to separate a single component of glycolipids, a large amount of repeated extraction is usually required, and the amount of extraction is small, which is difficult to meet the needs of further research on structural identification and biological activity of glycolipids.
Column chromatography
In recent years, column chromatographychromatographic columnThe separation method of glucose and lipid is widely used.For example, Chia Chung Hou et al. used folk Showa herb as raw material, extracted the phase with ethyl acetate, and used chloroform and methanol as eluents to carry out forward silica gel column chromatography to obtain fraction 8, and then took fraction 8 to carry out C18 reverse silica gel column chromatography again, and used 95% methanol as eluent to obtain glycerol glycolipids rich in linoleic acid.
Although column chromatography can deal with a large number of samples, it has many shortcomings, such as serious irreversible adsorption, low separation efficiency, long time consumption and large solvent consumption.
Because the difference between the same type of glycolipids is only reflected in the different composition of acyl fatty acids, and the molecular electrification, molecular polarity and other properties are very similar, it is difficult to separate a single glycolipid from a large number of mixed glycolipids with existing methods.Therefore, it is impossible to buy a single natural standard glycolipid from the chemical market. All major chemical companies and companies specializing in lipid standards can only provide TLC level mixed glycolipid standards.Only by studying the content and structure of each component in the mixed glycolipids, can the relevant research (such as biological activity) be more in-depth.Therefore, it is necessary to find a new method with low energy consumption, high separation efficiency and large amount of extraction of single component of sugar and lipid to meet the needs of neurobiological research and clinical application research.
Countercurrent chromatography is a liquid-liquid chromatography technology developed in the past 30 years[5]。One of its advantages is that it does not use solid adsorption materials, which can avoid the kind of chromatography technologyIrreversible adsorption, sample degradation and other defects;The second advantage is that the sample can be completely recovered.As a separation technology in the laboratory, countercurrent chromatography has shown thatHigh performance liquid chromatographyIncomparable advantages, such as low requirements for sample purity, large injection volume, simple operation, etc.
