Sheet #7 Lecture (Glycoproteins Lecture Part 1) Lecture Date :- 11-7-2018 Done & Edited By :- سندس نصار & Tasneem Al-Abbadi

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Complex Carbohydrates Glycosaminoglycans(GAGs) Glycoproteins and proteoglycans

LECTURE OUTLINE Differences between glycoproteins and proteoglycans Structures of glycoproteins and proteoglycans Functions of glycoproteins and proteoglycans Synthesis and degradation of glycoproteins and proteoglycans Pathology related to glycoproteins and proteoglycans

Differences Between Glycoproteins and Proteoglycans Proteins conjugated to saccharides lacking a serial repeat unit Glycoproteins Protein>>carbohydrate Proteins conjugated to polysaccharides with serial repeat units Glycosaminoglycans Mucopolysaccharides Carbohydrate>>protein Proteoglycans البروتينات اكثر من الكربوهيدرات ولا تحتوي على Glycoprotein نفس العيله لكن ال Serial repeat unit الكربوهيدرات اكثر من البروتينات وتحتوي على Proteoglycan بينما بال Serial repeat unit

Glycoprotein Glycoproteins are proteins that contain oligosaccharide chains (glycans) covalently attached to their polypeptide side-chains. The process of attaching the glycans is known as glycosalation. The sugar groups attached to glycoprotein can assist in protein folding or improve a proteins’ stability. ) ## addition of carbohydrates to protein ) ## Oligo means less than 10 units *few* ## Poly means a lot ,more than 100 *عديد* 6

Glycosalation : amino acid will be addition to it during modification Sheet 1 Glycosalation : amino acid will be addition to it during modification Hydroxyl protein is an modifying amino acid then it passes through hydroxylation by vitamin C We have a lot of factors that effect the protein folding like ; sugar groups ,bonds , interactions

The disaccharide units contain either of two modified sugars, called amino sugars N-acetylgalactosamine (GalNAc) or N-acetylglucosamine (GlcNAc), and an acidic sugar uronic acid such as glucuronic acid or iduronic acid. The amino group is usually acetylated.

In some glycosaminoglycans, one or more of the hydroxyls of the amino sugar is esterified with sulfate. The combination of these sulfate groups and the carboxylate groups of the uronic acid residues gives the glycosaminoglycans a very high density of negative charge. Keratan sulfate is an exception in which galactose is present, instead of an acidic sugar. Hyaluronic acid does not contain sulfate.

Sheet 2 We have hydroxyl amino acid and sulfate amino acid .. And we have a carbohydrate group which attached to amino acid and urinic acid to give negative charge

Structure of Glycosaminoglycans GAGs in the body are linked to core proteins ( except hyaluronic acid), forming proteoglycans (also called mucopolysaccharides). The GAGs extend perpendicularly from the core in a brush-like structure. e.g. in cartilage proteoglycan the GAGs present are chondriotin sulfate and keratan sulfate

Proteoglycan Aggregates Proteoglycan monomers associate with a molecule of hylauronic acid to form proteoglycan aggregates in association with linker proteins in a “bottle brush” arrangement. Association is not covalent but ionic between hyaluronic acid and the core protein. Stabilized by link proteins

Proteoglycan aggregate of the extracellular matrix ##The backbone ##Modified sugars One very long molecule of hyaluronan is associated noncovalently with about 100 molecules of the core protein aggrecan

Interactions between cells and the extracellular matrix with binding sites for both integrin and the proteoglycan

Linkage The linkage of GAGs to the protein core involves a specific trisaccharide composed of two galactose residues and a xylose residue (Gal-Gal-Xyl-O-CH2-protein).

The trisaccharide linker is coupled to the protein core through an O-glycosidic bond to a Serine residue in the protein. Some forms of keratan sulfates are linked to the protein core through an N-glycosidic bond. The protein cores of proteoglycans are rich in Serine and Threonine residues, which allows multiple GAG attachments. ##(both of them have hydroxyl amino acid )

STRUCTURE OF GLYCOPROTEINS One or more carbohydrate chains--covalently linked to a protein. The chains may be neutral or negatively charged. They are frequently branched. There are two types of glycosidic links: 1. O-glycosidic link O-glycosidic link between galactose or glucose and the hydroxyl group of hydroxylysine (i.e. collagen). Other O-linked glycoproteins have a glycosidic link between N-acetyl galactosamine and either serine or threonine (i.e. blood group substances and salivary mucins). 2. N-glycosidic link N-glycosidic links exist between N-acetylglucosamine and asparagine. There are two types: A. High mannose B. Complex. For example, in addition to mannose they may contain N-acetylglucosamine, galactose, fucose and N-acetylneuraminic acid (sialic acid)

Lippincott

Their core pentasaccharide is the same. In the complex form additional sugar residues are present: N-acetylglucosamine (GlcNAc) and N-acetylneuraminic acid (NANA). Fucose

Eight Sugars in Glycoproteins Abbreviation β-D-Glucose Glc β-D-Galactose Gal β-D-Mannose Man α-L-Fucose Fuc N-Acetylgalactosamine GalNAc N-Acetylglucosamine GlcNAc N-Acetylneuraminic acid NeuNAc Xylose Xyl

Glycoproteins Glycoproteins are proteins that contain oligosaccharide (glycan) chains covalently attached to their polypeptide backbones. Glycoproteins occur in most organisms, from bacteria to humans. Their carbohydrate content ranges from 1% to over 85% by weight.

They differ from proteoglycans: Length of the chain is relatively short (usually 2-10 sugar residues) very long in GAGs. Do not have repeating disaccharide units. They are branched. May or may not be negatively charged.

The distinction between proteoglycans and glycoproteins resides in the level and types of carbohydrate modification.

Proteoglycans also contain the sugar glucuronic acid (GlcA). The carbohydrate modifications found in glycoproteins are rarely as complex as that of proteoglycans. Most proteins that are secreted, or bound to the plasma membrane, are modified by carbohydrate attachment. The part that is modified, in plasma membrane-bound proteins, is the extracellular portion of the protein.

Intracellular proteins are less frequently modified by carbohydrate attachment. However, the attachment of carbohydrate to intracellular proteins confers unique functional activities on these proteins

Structure of Glycoprotein The oligosaccharide components of glycoproteins  is branched heteropolymers  composed of D-hexoses, with the addition in some cases of neuraminic acid, and of L-fucose (6-deoxyhexose)

FUNCTIONS

Function Glycoprotein Some Functions of Glycoproteins _________________________________________________ Function Glycoprotein 1. Structural molecule Collagens/Arthritis Proteins& modified sugars 2. Lubricant Mucins/ Peptic ulcer For protection 3. Transport molecule e.g. Transferrin, For iron Ceruloplasmin For copper 4. Immune system Immunoglobulins, Histocompatibility antigens, Blood group determinants 5. Hormone e.g. HCG, TSH ( + NH, NSH) fertilization مسؤول عن ال HCGهرمون ال chains و بختلفو بالبيتا Polypeptide chain الهرمونات بتشابهو بال 6. Enzymes e.g. Alkaline phosphatase 7. Blood clotting e.g. Fibrinogen 8. Blood groups 9. Cell surface recognition Lectins

Glycoproteins antibodies are glycoproteins Glycoproteins contain carbohydrate units covalently bonded to a polypeptide chain antibodies are glycoproteins carbohydrates play a role as antigenic determinants, the portions of the antigenic molecule that antibodies recognize and to which they bond.

Almost all the plasma proteins of humans—except albumin—are glycoproteins. For example, O-linked oligosaccharides on the surface of RBCs help provide the ABO blood group determinants Many proteins of cellular membranes contain substantial amounts of carbohydrate.

Blood Group Substances Membranes of animal plasma cells have large numbers of relatively small carbohydrates bound to them: these membrane-bound carbohydrates act as antigenic determinants among the first antigenic determinants discovered were the blood group substances in the ABO system, individuals are classified according to four blood types: A, B, AB, and O at the cellular level, the biochemical basis for this classification is a group of relatively small membrane-bound carbohydrates

ABO Blood Classification ( يستقبل من الكل)Gal & GalNAcيحتوي ال *AB*ال

ABO Blood Classification in type A, the nonreducing end is NAGal in type B it is Gal in type AB, both types are present in Type O, neither of these terminal residues is present

Recognition and adhesion at the cell surface ( وتتحد معهاtoxin, viruses ,,وتتعرف على اي من ال recognition site (الهدف من الجلايكوبروتين انها تكون

Stronger interaction near the site of inflammation lectin-ligand interactions in lymphocyte movement to the site of an infection Stronger interaction near the site of inflammation

Helicobacter pylori Interaction between a bacterial surface lectin and an oligosaccharide of the gastric epithelium

Helicobacter : bacterial surface It’s cause ulcers of stomach Sheet 3 Helicobacter : bacterial surface It’s cause ulcers of stomach Acid media in stomach = 2.5 It has been shown to be treated by antibiotics rather than by antiacidic It may be convert to cancer

معلومة من خارج كلام الدكتور H. pylori is a common type of bacteria that grows in the digestive tract  and has a tendency to attack the stomach lining. It infects the stomachs of roughly 60 % of the world’s adult population. H. pylori infections are usually harmless, but they’re responsible for the majority of ulcers in the stomach and small intestine.

The extracellular space in animal tissues is filled with a gel-like material, the extracellular matrix, also called ground substance, which holds the cells of a tissue together and provides a porous pathway for the diffusion of nutrients and oxygen to individual cells.

extra- cellular matrix Epithelial cells extra- cellular matrix Underlying cells

Extracellular matrix = ground substance It’s contain glycoproteins Sheet 4 Extracellular matrix = ground substance It’s contain glycoproteins It’s passage pathway for nucleus component

The extracellular matrix is composed of an interlocking meshwork of heteropolysaccharides and fibrous proteins. Heteropolysaccharides in the body are the glycosaminoglycans (GAGs). These molecules are long unbranched polysaccharides containing a repeating disaccharide unit.

GAGs are highly negatively charged molecules, with extended conformation that imparts high viscosity to the solution. Important function GAGs are located primarily on the surface of cells or in the extracellular matrix (ECM).

Along with the high viscosity of GAGs comes low compressibility, which makes these molecules ideal for a lubricating fluid in the joints. Work as shock absorption At the same time, their rigidity provides structural integrity to cells and provides passage ways between cells, allowing for cell migration.

Hyaluronic acid Hyaluronic acid is unique among the GAGs in that it does not contain any sulfate and is not found covalently attached to proteins as a proteoglycan. It is, however, a component of non-covalently formed complexes with proteoglycans in the ECM.

Only GAG present both in animals and bacteria. Found in synovial fluid, vitreous humor, ECM of loose connective tissue Umbilical cord Cartilage

All of this to make move easy and flexible Sheet 5 All of this to make move easy and flexible Synovial fluid : found in the cavities of synovial joints vitreous humor : refers to eye

Glycosaminoglycans b-1,3 b-1,4 GlcUA GlcNAc No protein link No sulfate 12/1/2018 Glycosaminoglycans b-1,3 b-1,4 GlcUA GlcNAc No protein link No sulfate b-1,3 glycosidic linkage Hyaluronate GlcUA: glucuronic acid GlcNAc: N-acetylglucosamine

Specific function: 1.Hyaluronic acid is especially high in concentration in embryonic tissues and is thought to play an important role in permitting cell migration during morphogenesis and wound repair. 2. Act as lubricators and shock absorbers.

Association with major diseases: Hyaluronic acid may be important in permitting tumor cells to migrate through the ECM. Tumor cells can induce fibroblasts to synthesize greatly increased amounts of this GAG, thereby perhaps facilitating their own spread.

Sheet 6 We have two types of tumor A tumor remains in place and this type is not serious(dangerous) wherever it is . The tumor that spreads and does not remain constant : cancer cells migrate from their place and when it reach in lung for example it’s become difficult for treatment And causing perforation membrane in cells

Glycosaminoglycans b-1,3 b-1,4 GlcUA GalNAc 12/1/2018 Glycosaminoglycans b-1,3 b-1,4 GlcUA GalNAc GlcUA-Gal-Gal-Xyl-O-Ser link Sulfate at 4 or 6 C of GalNAc b-1,3 glycosidic linkage Chondroitin sulfate GlcUA: glucuronic acid Gal: galactose Xyl: xylose Ser: serine GalNAc: N-acetylgalactosamine

Chondroitin sulfate Most abundant GAG Cartilage (bind collagen and hold the fibers strongly) Tendons Ligaments Heart valves

Glycosaminoglycans a-1,4 a-1,4 GlcUA GlcNAc GlcN and GlcUA or IdUA 12/1/2018 Glycosaminoglycans a-1,4 a-1,4 GlcUA GlcNAc GlcN and GlcUA or IdUA N and O sulfate (C2,3,6) a-1,4 glycosidic linkage Heparin GlcN: glucosamine GlcUA: glucuronic acid IdUA: iduronic acid NAc: N-acetyl > NAc < N and O sulfate Heparan sulfate

Heparan sulfate Extracellular GAG contains higher acetylated glucosamine than heparin And less sulphated groups found in the basement membrane of the kidney along with type IV collagen and laminin where it plays a major role in determining the charge selectiveness of glomerular filtration

are associated with the plasma membrane of cells, with their core proteins actually spanning that membrane. In it they may act as receptors and may also participate in the mediation of cell growth and cell-cell communication.

Association with the disease: Some tumor cells have less heparan sulfate at their surfaces, and this may play a role in the lack of adhesiveness that these cells display.

Heparin The repeating unit of heparin

Heparin It is an intracellular GAG. Component of intracellular granules of mast cells lining the arteries of the lungs, liver and skin more sulfated than heparan sulfate

Heparin is an important anticoagulant Heparin is an important anticoagulant. It binds with factors IX and XI, but its most important interaction is with plasma antithrombin III. Heparin can also bind specifically to lipoprotein lipase present in capillary walls, causing a release of this enzyme into the circulation.

Sheet 7 In heart surgery such as aschemia the patient should take heparin or warfarin

Specific function: Heparin and warfarin are widely used in the treatment of thrombotic and thromboembolic conditions, such as deep vein thrombosis and pulmonary embolus. Heparin is administered first, because of its prompt onset of action, whereas warfarin takes several days to reach full effect. Their effects are closely monitored by use of appropriate tests of coagulation because of the risk of producing hemorrhage.

Glycosaminoglycans b-1,3 b-1,4 IdUA GalNAc IdUA with some GlcUA 12/1/2018 Glycosaminoglycans b-1,3 b-1,4 IdUA GalNAc IdUA with some GlcUA Sulfate at 4 or 6 C of GalNAc b-1,3 glycosidic linkage Dermatan sulfate IdUA: iduronic acid GlcUA: glucuronic acid GalNAc: N-acetylgalactosamine

Dermatan sulfate Sclera- gives shape to the eye. Binds LDL –plays a role in the development of atherosclerosis. skin, blood vessels, heart valves

Glycosaminoglycans b-1,4 b-1,3 GlcUA GlcNAc GlcNAc and Gal (no UA) 12/1/2018 Glycosaminoglycans b-1,4 b-1,3 GlcUA GlcNAc GlcNAc and Gal (no UA) Sulfate on C6 of Gal or HexN b-1,4 glycosidic linkage Keratan sulfate I GlcNAc: N-acetylglucosamine Gal: galactose UA: uronic acid HexN: hexosamine GalNAc: N-acetylgalactosamine Ser: serine Thr: threonine GlcUA: glucuronic acid Keratan sulfate II GalNAc-O-Ser or Thr

Keratan sulfate cornea, bone, cartilage aggregated with chondroitin sulfates

Both keratan sulfate I and dermatan sulfate are present in the cornea Both keratan sulfate I and dermatan sulfate are present in the cornea. They lie between collagen fibrils and play a critical role in corneal transparency.

In various types of arthritis, proteoglycans may act as autoantigens, thus contributing to the pathologic features of these conditions. The amount of chondroitin sulfate in cartilage diminishes with age.

When chondroitin sulfate decrease it causes to difficult in walk Sheet 8 When chondroitin sulfate decrease it causes to difficult in walk

Whereas the amounts of keratan sulfate and hyaluronic acid increase. These changes may contribute to the development of osteoarthritis. Osteoarthritis: inflammation of the bone Changes in the amounts of certain GAGs in the skin are also observed with aging.

glycosaminoglycans of extracellular matrix lubricants in the synovial fluid of joints cartilage, tendons, ligaments a variety of horny structures formed of dead cells: horn, hair, hoofs, nails

The End Of The Lecture & Sheet But Not The Subject