CINXE.COM

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head><script type="text/javascript" src="https://web-static.archive.org/_static/js/bundle-playback.js?v=7YQSqjSh" charset="utf-8"></script> <script type="text/javascript" src="https://web-static.archive.org/_static/js/wombat.js?v=txqj7nKC" charset="utf-8"></script> <script>window.RufflePlayer=window.RufflePlayer||{};window.RufflePlayer.config={"autoplay":"on","unmuteOverlay":"hidden"};</script> <script type="text/javascript" src="https://web-static.archive.org/_static/js/ruffle/ruffle.js"></script> <script type="text/javascript"> __wm.init("https://web.archive.org/web"); __wm.wombat("http://faculty.virginia.edu:80/mcgarveylab/Carbsyn/Carblist/html/disacch.html","20181118183515","https://web.archive.org/","web","https://web-static.archive.org/_static/", "1542566115"); </script> <link rel="stylesheet" type="text/css" href="https://web-static.archive.org/_static/css/banner-styles.css?v=p7PEIJWi" /> <link rel="stylesheet" type="text/css" href="https://web-static.archive.org/_static/css/iconochive.css?v=3PDvdIFv" />   <link rel="stylesheet" type="text/css" href="https://web.archive.org/web/20181118183515cs_/http://localhost/css/sugars.css"/>  <meta http-equiv="content-type" content="text/html; charset=utf-8"/>  <title>Disaccharides and Oligiosaccharides</title> </head> <body> <div id="intro"><h1>Disaccharides and Oligiosaccharides</h1></div> <div id="text"> <p>This section is divided into the reducing and non-reducing types of disaccharide. If two monosaccharides are linked through their anomeric centers the disaccharide formed is a <i>non-reducing</i> disaccharide. If one monosaccharide is linked by one of its other hydroxyl groups, then the anomeric center is unsubstituted and a <i>reducing</i> disaccharide occurs. Two monosaccharides have many more ways of connecting to form a reducing disaccharide than a non-reducing disaccharide.</p> <table id="picdef"> <tr><td id="heading" colspan="2"><h1>Reducing Disaccharides</h1></td></tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/cellobiose.gif" width="278" height="103"/>  </td> <td><em>Cellobiose</em> (4-<i>O</i>-β-<small>D</small>-glucopyranosyl-<small>D</small>-glucose) results from the hydrolysis of cellulose by bacteria. Mammals lack the necessary enzymes—cellobiohydrolases and <i>endo</i>-cellulases—to hydrolyze cellulose. Cellobiose constitutes materials such as cotton and paper. <i>Maltose</i> is a homopolmyer of cellobiose.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/gentiobiose.gif" width="229" height="136"/></td> <td><em>Gentiobiose</em> (6-<i>O</i>-β-<small>D</small>-glucopyranosyl-<small>D</small>-glucose) is found in many glycosides such as amygdalin.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/isomaltose.gif" width="209" height="155"/></td> <td><em>Isomaltose</em> (6-<i>O</i>-α-<small>D</small>-glucopyranosyl-<small>D</small>-glucose) is formed from two glucose monosaccharides. It is often found at the branching points of amylopectin and glycogen.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/lactose.gif" width="261" height="88"/></td> <td><em>Lactose</em> (4-<i>O</i>-β-<small>D</small>-galactopyranosyl-<small>D</small>-glucose) is the predominant disaccharide found in milk. <i>Lactose intolerance</i> is a condition in which there is a lack of the enzyme lactase. <i>Galactosaemia</i> is a condition that results from an inability to process the D-galactose after hydrolysis.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/laminaribiose.gif" width="268" height="89"/></td> <td><em>Laminaribiose</em> is a polysaccharide building unit for laminarin (brown algae), pachyman (fungi), paramylon (unicellular algae), and callose.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/maltose.gif" width="255" height="130"/></td> <td><em>Maltose</em> (4-<i>O</i>-α-<small>D</small>-glucopyranosyl-<small>D</small>-glucose) results from hydrolysis of starch by enzymes (amylases) in the mammalian digestive tract. Notice that the glycosidic linkage is α and that of the homopolymer <i>cellobiose</i> is a β linkage. Maltose is used as a sweetner and as a substrate for fermentation. It is also the constituent of the polymer <i>amylose</i>.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/mannobiose.gif" width="277" height="76"/></td> <td><em>Mannobiose</em> is the unit for the plant polysaccharide mannan.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/xylobiose.gif" width="278" height="65"/></td> <td><em>Xylobiose</em> is the unit found in many polysaccharides such as the xylans that constitute plant cell walls.</td> </tr> <tr><td colspan="2"> </td></tr> <tr><td id="heading"><h1>Non-Reducing Disaccharides</h1></td></tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/sucrose.gif" width="164" height="185"/></td> <td><em>Sucrose</em> (β-D-fructofuranosyl α-D-glucopyranoside) is the predominant disaccharide found in sugar cane and sugar beet. It is a well known sweetner and has a five-membered furanosyl unit. 10<sup>8</sup> tons of sucrose are produced annually for consumption.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/poly/trehalose.gif" width="157" height="193"/></td> <td><em>Trehalose</em> (α-D-glucopyranosyl α-D-glucopyranoside) is found in microbes, fungi, and certain insects. One isomer is <i>neotrehalose</i> with an α,β link. Another isomer is <i>isotrehalose</i> which has a β,β link.</td> </tr> <tr><td colspan="2"> </td></tr> <tr><td colspan="2"><h1>Oligiosaccharides</h1></td></tr> <tr><td colspan="2">Many oligiosaccharides are not found as isolated molecules. Instead, they may be attached to other biomolecules (glycoconjugates). Glycoconjugates of proteins and various lipids are especially likely. For example, the lipids on the surface of erythrocytes are conjugated with various oligiosaccharides. The oligiosaccharides are involved in cellular recognition and are responsible for the blood group serotype (A, B, AB, and O).</td></tr> <tr><td colspan="2"><em>α-, β-, and γ-cyclodextrins</em> are a class of cyclic oligosaccharides that contain from six to eight monosaccharides. Since they are derived from starch, the units are all D-glucopyranose saccharides. They are held together by an α-1,4 linkage. Ligands are able to attach by partitioning into the hydrophobic interior of the cyclodextrin.</td></tr> <tr><td colspan="2"><em>Raffinose</em> is a D-galactosylated version of sucrose: α-D-galactopyranosyl-(1→6)-α-D-glucopyranosyl β-D-fructofuranoside. It is more convenient to abbreviate this long name as α-D-Gal<i>p</i>-(1→6)-α-D-Glc<i>p</i>-(1↔2)-β-D-Fru<i>f</i>.</td></tr> <tr><td colspan="2"> </td></tr> <tr><td colspan="2"><h1>Polysaccharides</h1></td></tr> <tr><td colspan="2"><em>Amylopectin</em> is a high molecular weight (~10<sup>8</sup> a.u.) polymer consisting of repeating units of maltose. For about every ten maltose units, branching [(1→6)-α-] occurs. Because of this branching, amylopectin is globular-shaped and non-crystalline.</td></tr> <tr><td colspan="2"><em>Amylose</em> has a lower molecular weight (~10<sup>6</sup> a.u.) than amylopectin. Maltose is the repeating unit with (1→4)-α-D linkages. This causes the semi-crystalline polysaccharide to assume a helical tube-like shape. The shape of amylose is able to accept iodine as a ligand. This interaction causes the blue coloration of starch in the presence of iodine.</td></tr> <tr><td colspan="2"><em>Cellulose</em> is the most abundant polymer on Earth. Cellulose is a major structural constituent of plant cell walls. It is a polymer of cellobiose units. Because of the β linkage, humans cannot hydrolize cellulose. In contrast, the α linkage of starch is succeptible to hydrolysis by enzymes in humans. The polymer shape of cellulose is similar to a twisted ribbon and is influenced by hydrogen bonding. This hydrogen bonding may be parallel or anti-parallel thus giving cellulose I and cellulose II. As a result, these "twisted ribbons" form fibers that give form and structure. Because of its fibrous structure, cellulose is used extensively in the paper industry.</td></tr> <tr><td colspan="2"><em>Chitin</em> is to the animal kingdom that cellulose is to the plant kingdom. Chitin is found in shells of crustaceans and in the exoskeleton of insects. Chitin is a polymer of <i>N</i>-acetyl-D-glucosamine with <i>N<sup>I</sup></i>,<i>N<sup>II</sup></i>-diacetylchitobiose being the repeating unit. Like cellulose, intramolecular hydrogen bonding is important for the structure of chitin.</td></tr> <tr><td colspan="2"><em>Glycogen</em> is the mammalian version of starch. Its structure is similar to amylopectin except for glycogen's more frequent branching (five instead of every eight). Its molecular weight is therefore usually higher than amylopectin. Glycogen phosphorylase and other various debranching enzymes combine to produce the D-glucose 1-phosphate needed for the glycolysis sequence.</td></tr> <tr><td colspan="2"><em>Heparin</em> is a heteropolysaccharide with anti-clotting properties. It has medicinal value for surgury and is used to treat thrombosis. Heparin is found in arterial walls where it facillitates interactions between antithrombin (an inhibitor of blood coagulation) and thrombin (a clot-forming protein).</td></tr> <tr><td colspan="2"><em>Starch</em> is produced by plants and is stored as granules for later use as energy. Starch is a 1 to 4 mixture of amylose and amylopectin.</td></tr> <tr><td colspan="2"> </td></tr> <tr><td colspan="2"><h1><i>O</i>-Glycosides</h1></td></tr> <tr><td colspan="2">The disaccharides shown above are all <i>O</i>-glycosides. A glycosidic bond may also involve non-saccharide compounds such as phenols.</td></tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/misc/arbutin.gif" width="213" height="102"/></td> <td><em>Arbutin</em> is found in the leaves of <i>Rosaceae</i> and, when hydrolyzed, produces hydroquinone. This compound therefore has strong reducing properties that have biochemical consequences.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/misc/amygdalin.gif" width="265" height="128"/></td> <td><em>Amygdalin</em> is isolated as one of the components of the seeds of <i>Rosaceae</i>. Upon enzymatic hydrolysis hydrogen cyanide is evolved. It also has strong biochemical consequences.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/misc/erythromycin.gif" width="244" height="214"/></td> <td><em>Erythromycin A</em> is a macrolide that has whithin its structure the amino saccharide <small>D</small>-desosamine and the branched saccharide <small>L</small>-cladinose. It inhibits protein synthesis by bactereial ribosomes.</td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/misc/streptomycin.gif" width="172" height="253"/></td> <td><em>Streptomycin</em> also intereferes with bacterial peptide synthesis by binding to sites on the ribosomes. It is part of the aminoglycoside family of antibiotics. The saccharide derivatives in streptomycin include the formylpentose <small>L</small>-streptose as well as the rarely seen 2-deoxy-2-methylamino-<small>L</small>-glucose. One of the uses of streptomycin is to treat tuberculosis</td>. <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/misc/adriamycin.gif" width="208" height="181"/></td> <td><em>Adriamycin</em> along with the related <i>daunomycin</i> are anthracyclines possessing anti-Gram-positive activity. They also have anticancer properties towards soft-tissue sarcomas and leukaemias. This is probably due to their intercalating behavior towards DNA which results in the inhibition of RNA and ultimately protein synthesis. <small>L</small>-duanosamine is the saccharide unit found in each.</td></tr> <tr><td colspan="2"> </td></tr> <tr> <td colspan="2"><h1><i>N</i>-Glycosides</h1></td> </tr> <tr> <td colspan="2">Glycosylamines have important roles in biochemistry since most peptide-carbohydrate linkages are of the <i>N</i>-glycosidic type. These linkages usually involve <small>D</small>-glucosamine bonding to the <small>L</small>-asparagine amido group. <small>D</small>-ribose and 2-deoxy-<small>D</small>-ribose can form <i>N</i>-glycosidic bonds with purine and pyrimidine bases to create nucleotides. This is very significant because nucleotides are components of both DNA and RNA.</td></tr></td> </tr> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/misc/streptothricin.gif" width="224" height="171"/></td> <td><em>Streptothricin F</em> displays activity against both Gram-negative and Gram-positive bacteria. The aminosaccharide is derived from 2-amino-2-deoxy-<small>D</small>-gulose.</td> </tr> </table> <h1><i>C</i>-Glycosides</h1> <p id="noindent">In a strict sense these compounds do not have glycosidic bonds. Substituting carbon for the anomeric oxygen of the saccharide destroys the anomeric acetal and renders the molecule stable to acids. This is different than the usual glycosidic bonds involving heteroatoms. The two natural products shown below each have a <i>C</i>-glycosidic bond.</p> <table id="wide"> <tr> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/misc/aquayamycin.gif" width="282" height="109"/></td> <td><img src="/web/20181118183515im_/http://faculty.virginia.edu/mcgarveylab/Carbsyn/Carblist/img/misc/showdomycin.gif" width="105" height="116"/></td> </tr> <tr> <td>aquayamycin</td> <td>showdomycin</td> </tr> <tr><td> </td><td> </td></tr> </table> </div> <div id="text"> <h1>Related Pages</h1> <ul> <li><a href="start.html">Introduction</a></li> <li><a href="aldoses.html">Aldose Forms</a></li> <li><a href="ketoses.html">Ketose Forms</a></li> <li><a href="pyranose.html">Pyranose Forms</a></li> <li><a href="furanose.html">Furanose Forms</a></li> </ul> </div> </body> </html>