第一章 糖(1).ppt

Biochemistry,School of life science and technologyLi Wenzhe,1.Existence Carbohydrates are the most abundant biomolecules on earth.2.Saccharides play a variety of roles in living organisms:Energy storage(monosaccharides and oligosaccharides and polysaccharides)Structural roles(polysaccharides)Cell identity(oligosaccharides),Carbohydrate/Saccharides,3.Definition and classification of saccharide,Carbohydrates are polyhydroxy aldehydes or ketones,or substances that yield such compounds on hydrolysis.Empirical formula(CH2O)n;some also contain nitrogen,phosphorus,or sulfur.,Classification of saccharide,Three major size classes of carbohydrates:MonosaccharidesSaccharide Oligosaccharides Polysaccharides:homopolysaccharide,heteropolysaccharide,glycoconjugate,4.Structure of monosaccharide,Straight-chain structure of monosaccharide,carbonyl group：醛糖aldose,酮糖ketosecarbon atoms in the backbone：3,4,5,6,7 trioses,tetroses,pentoses,hexoses,and heptoses,不对称碳原子(asymmetric carbon atom),C*（chiral carbon）,Fisher projection,单糖构型configuration,D，L nomenclature,The enantiomers 对映异构体 of glyceraldehyde,Configuration of monosaccharide:based on 甘油醛 glyceraldehyde Compare the configuration of the chiral center most distant from the carbonyl carbon.,Optically active isomers旋光异构,Monosaccharide has optical activity单糖具有旋光性左旋(levorotatory),“-”右旋(dextrorotatory),“+”旋光率(specific rotation),D、L mean configuration构型+、-mean the optical activityThe predominant monosaccharides in nature-D configuration.,Cyclic/Ring structure of monosaccharide环状半缩醛,Formation of hemiacetals and hemiketals.,Fisher projection formula to Haworth perspective formulas,/异头物anomer,-变旋现象(mutarotation)D,L,异头碳,Pyranose吡喃糖,Furanose呋喃糖,5.The conformation of monosaccharide单糖的构象 Pyranose：,Boat Chair,Conformation of furanose:Envelope form,6.Monosaccharides Are Reducing Agentscan be oxidized by ferric(Fe3+)or cupric(Cu2+)ion.Reducing sugars Fehlings reaction,葡萄糖酸内酯,7.Important monosaccharides and derivatives,Six carbon sugarProvide a rapid source of ATPPolymer form:Starch,cellulose-plants Glycogen-animals,Fructose:ketohexose Free sugar in many fruits Derived from hydrolysis of sucrose,Galactose Both the D and L forms are found in nature.Commonly found in milk as part of the disaccharide lactose L-Galactose is present in polysaccharides,such as agar,Derivatives of monosaccharides,Monosaccharides can be chemically altered in several ways to provide new classes of compounds deoxy sugar 脱氧糖（羟基被氢原子取代）sugar acids 糖酸（醛基或伯醇基被氧化）alditols 糖醇（羰基被还原）amino sugars 氨基糖（分子中的一个羟基被氨 基取代）Sugar esters 糖脂（分子中的羟基与其他基团形成酯键）,岩藻糖 鼠李糖 6-脱氧-L-Gal 6-脱氧-L-Man,葡萄糖醛酸 葡萄糖酸 葡萄糖内酯,uronic acid糖醛酸 aldonic acid醛糖酸,半乳糖胺 甘露糖胺,Sugar Esters,Phosphate esters are important metabolic intermediates：utility,activityThe ribose moiety of nucleotides such as ATP is phosphorylated at the 5-position,8.Oligosaccharide,Maltose 麦芽糖：reducing disaccharides,Reducing end,A product of starch degradation,Glycosidic bond,Nomenclature of disaccharide.,O-,O-,O-,sucrose蔗糖：Glucose-fructoseNonreducing sugar,sucrose,formed by plants but not by animalsintermediate product of photosynthesisprincipal form in which sugar is transported from the leaves to other parts of the plant bodyhigh solubility Protective effects of most biomolecules,Lactose 乳糖,Galactose-glucose,Lactose,occurs naturally only in milk,5%in milk,a reducing disaccharide.Nutrition for infantsLactase and lactose intolerance,9.多糖 polysaccharide,Polymers of monosaccharide units Homopolysaccharides同多糖 Heteropolysaccharides杂多糖,Difference,Comopsition of the monomeric unitThe linkages between themThe ways in which branches from the chains occur.,Storage polysaccharides:starch,glycogen Structural polysaccharides cellulose chitin Glycosaminoglycans 粘多糖 Proteoglycan蛋白聚糖 complex Bacterial cell wall,amylose 直链淀粉（14）GlucoseStarch淀粉 amylopectin 支链淀粉（14）Glc（16）GlcGlycogen糖原:（14）and（16）Glc,starch store in cells with“granule”form,淀粉颗粒,The secondary structure of amylose:helix,A cluster of amylose and amylopectin to occur in starch granules.,Store in animal liver or muscle cells.,Glycogen,Structure of glycogen,Similar to that of amylopectinDifference:highly branched-why?chains are shorter more compactWhy not store glucose in its monomeric form?,Cellulose 作为植物的骨架,目 录,习题11,Most animals cannot digest celluloseOnly ruminants 反刍动物 contain a symbiotic bacterium with cellulaseFungi too contain cellulase,N-acetyl-D-glucosamine,1 4 bonds algae,fungi,arthropods（节肢动物）,mollusks（软体动物）,and insects.,Chitin kaitin壳多糖,Chitin is the second most abundant polysaccharide on earth.,A beetle,Dextrans,bacterial and yeast polysaccharides made up of(1-6)-linked poly-D-glucose;have(1-3)branches,(1-2)or(1-4)branches.Dental plaque,formed by bacteria growing on the surface of teeth,is rich in dextrans.Synthetic dextrans(Sephadex)-size-exclusion chromatography,Agar,agaroseagar,10.Heteropolysaccharides in bacterial cell walls,Bacterial cell wallsGram-positive bacteria cross-linked multilayered peptideoglycan肽聚糖，layered on top of a lipid bilayer membranePeptides covalently link N-acetylmuramic acidThe mixture of L and D amino acids in the peptidesHave a pentaglycine chain in the cross-linkTeichoic acid 磷壁酸Eg.Sraphylococcus aureus 葡萄状球菌,penicillin,peptidoglycan,组成肽聚糖的重复单元：Muropeptide胞壁肽 Oligopeptide:four residues NAG(GlcNAc)N-乙酰葡糖胺 Disaccharide NAM(MurNAc)N-乙酰胞壁酸,Muropeptide 胞壁肽,Gram-negative bacteriaA single layer of peptidoglycan sandwiched between outer and inner lipid bilayer membranesLack the pentaglycineThe terminal D-Ala residue of one tetrapeptide is attached directly to a neighboring tetrapeptide through either L-Lys or a lysine-like amino acid脂多糖 Eg.Escherichia.coli,11.Glycosaminoglycans 粘多糖，糖胺聚糖-Heteropolysaccharides of the extracellular matrix 软骨、腱等结缔组织中的结构多糖 糖醛酸己糖胺n n=30-250 uronic acid 糖醛酸Amine derivatives of hexoses 己糖胺,The repeating unit carries a carboxyl group often one or more sulfates-acidic,Have a high density of negative charges-extend conformation in solution.,Often combined with protein to form proteoglycans-an important component of the extracelluar matrix of vertebrates,Glycosaminoglycans functions:,Extracellular matrix of skin and connective tissueViscosity Hydrophilic Lubrication in joints Anticoagulant 抗凝血剂,hyaluronic acid contains alternating residues of D-glucuronic acid and N-acetylglucosamine.form clear,highly viscous solutions that serve as lubricants in the joints and eyes.an essential component of the extracellular matrix.Hyaluronidase-pathogenic bacteria infection sperm penetrating into ovum.,Chondroitin 4-sulfate 硫酸软骨素Keratan sulfate硫酸角质素,Heparin肝素 activate antithrombin-Anticoagulant 抗凝血,One very long molecule of HAabout 100 molecules of the core protein aggrecanContains many covalently bound CS and KS chainsLink proteins mediate the core protein-HA interaction,12.Proteoglycan aggregates蛋白聚糖,Trisaccharide linker-connects a glycosaminoglycan to a Ser residue in the core protein,Trisaccharide linker,整合素,蛋白聚糖,纤维连接蛋白,纠结的胶原蛋白,13.Cell identity:Lectin-Oligosaccharides,Oligosaccharides are enormously rich in structural information:20 different subunits for construction of hexamer-oligonucleotides:4,096(46)-polypeptides:6.4107(206)-oligosaccharides:1.441015 possibilitiessugar codereadable by the proteins thatinteract with it.,Lectins Are Proteins That Read the Sugar Code and Mediate Many Biological Processes,Movement of T lymphocytes to a site of inflammationSelectins are a family of plasma membrane lectinsP-selectin stored in the membranes of secretory granules.Whenendothelial cells are activated by thrombin,P-selectin translocated to theplasma membrane.,lectins mediate bacterial adhesion to host cells or toxin entry into cells.Eg：gastric ulcers胃溃疡 Helicobacter pylori幽门螺杆菌H.pylori has lectinsGastric epithelium has oligosaccharide LebLeb:part of type O blood group determinant,Understanding the details of the oligosaccharide binding sites of lectins allows:a.drug development b.vaccine development Lectins bind to carbohydrates with high affinity and specificity,Establishing the complete structure,branching positionsthe sequence in each branchthe configuration of each monosaccharide unitthe positions of the glycosidic糖苷links,a more complex problem than protein and nucleic acid analysis,14.Working with Carbohydrates(oligosaccharides and polysaccharides),polysaccharides are usually determined by acombination of methods,specific enzymatic hydrolysis-produce smaller fragments methylation analysis-locate bonds糖苷键stepwise degradation-determine sequenceconfiguration of anomeric carbons异头碳,Mass spectrometry and NMR spectroscopysmall samples of carbohydrate,sequenceconfiguration of carbonpositions of glycosidic bonds,内切糖苷酶,PNG酶F-GlcNAc AsnO-糖苷酶-GalNAc Ser/Thr,The oligosaccharide moieties of glycoproteins or glycolipids can be released by purified enzymesglycosidases.,内切糖苷酶,1,