885d_c07-238-27211/21/037:38 AM Page246Mac113mac113:1aEDL 246 Part I Structure and Catalysis nonreducing residue; to distinguish five- and six-mem- many plants it is the principal form in which sugar is bered ring structures, insert"furano"or "pyrano"into transported from the leaves to other parts of the plant the name. B)Indicate in parentheses the two carbon body. Trehalose, Glc(alelaGlc(Fig 7-12)-a disac atoms joined by the glycosidic bond, with an arrow con- charide of D-glucose that, like sucrose, is a nonreducing necting the two numbers; for example, (1-4)shows sugar--is a major constituent of the circulating fluid that C-1 of the first-named sugar residue is joined to (hemolymph) of insects, serving as an energy-storage C-4 of the second. (4) Name the second residue. If there compound is a third residue, describe the second glycosidic bond by the same conventions. (To shorten the description CH2O CH2OH of complex polysaccharides, three-letter abbreviations for the monosaccharides are often used, as given in Table 7-1. Following this convention for naming oligosaccharides, maltose is a-D-glucopyranosyl-(1-4) D-glucopyranose. Because most sugars encountered in this book are the d enantiomers and the pyranose form Lactose(B form) of hexoses predominates, we generally use a shortened B-D-galactopyranosyl-(1-4)-B-D-glucopyranose version of the formal name of such compounds, giving Ga(B1→4)Glc the configuration of the anomeric carbon and naming the carbons joined by the glycosidic bond. In this ab- CH.OHI breviated nomenclature, maltose is Glc(a1-4)Glc. The disaccharide lactose (Fig. 7-12), which yields BRH HO D-galactose and D-glucose on hydrolysis, occurs natu- loHI rally only in milk. The anomeric carbon of the glucose residue is available for oxidation. and thus lactose is a reducing disaccharide. Its abbreviated name is a-D-glucopyranosyl B-D-fructofuranoside Gal(Bl-4)Glc. Sucrose(table sugar)is a disaccharide Glc(a1+2B)Fru of glucose and fructose. It is formed by plants but not by animals. In contrast to maltose and lactose, sucrose CH2OH contains no free anomeric carbon atom. the anomeric carbons of both monosaccharide units are involved in H the glycosidic bond(Fig. 7-12). Sucrose is therefore a HO nonreducing sugar. Nonreducing disaccharides are named as glycosides; in this case, the positions joined are the anomeric carbons. In the abbreviated nomen- clature, a double-headed arrow connects the symbols ucopyra Glda1-1aGlc specifying the anomeric carbons and their configura- tions. For example, the abbreviated name of sucrose FIGURE 7-12 Some common disaccharides. Like maltose in Figure is either Gle(al+2B)Fru or Fru(B26laGlc Sucrose 7-11, these are shown as Haworth perspectives. The common name, is a major intermediate product of photosynthesis; in full systematic name, and abbreviation are given for each disaccharide TABLE 7-1 Abbreviations for common monosaccharides and some of their derivatives Abequose Glucuronic acid GIcA Galactosamine Glucosamine N-Acetylgalactosamine N-Acetylglucosamine GICNAc Iduronic acid Mannose Muramic acid Rhamnose N-Acetylmuramic acid Mur2Ac N-Acetylneuraminic acid Neu5Ac Xylose (a sialic acid)nonreducing residue; to distinguish five- and six-mem￾bered ring structures, insert “furano” or “pyrano” into the name. (3) Indicate in parentheses the two carbon atoms joined by the glycosidic bond, with an arrow con￾necting the two numbers; for example, (1n4) shows that C-1 of the first-named sugar residue is joined to C-4 of the second. (4) Name the second residue. If there is a third residue, describe the second glycosidic bond by the same conventions. (To shorten the description of complex polysaccharides, three-letter abbreviations for the monosaccharides are often used, as given in Table 7–1.) Following this convention for naming oligosaccharides, maltose is
-D-glucopyranosyl-(1n4)- D-glucopyranose. Because most sugars encountered in this book are the D enantiomers and the pyranose form of hexoses predominates, we generally use a shortened version of the formal name of such compounds, giving the configuration of the anomeric carbon and naming the carbons joined by the glycosidic bond. In this ab￾breviated nomenclature, maltose is Glc(
1n4)Glc. The disaccharide lactose (Fig. 7–12), which yields D-galactose and D-glucose on hydrolysis, occurs natu￾rally only in milk. The anomeric carbon of the glucose residue is available for oxidation, and thus lactose is a reducing disaccharide. Its abbreviated name is Gal(1n4)Glc. Sucrose (table sugar) is a disaccharide of glucose and fructose. It is formed by plants but not by animals. In contrast to maltose and lactose, sucrose contains no free anomeric carbon atom; the anomeric carbons of both monosaccharide units are involved in the glycosidic bond (Fig. 7–12). Sucrose is therefore a nonreducing sugar. Nonreducing disaccharides are named as glycosides; in this case, the positions joined are the anomeric carbons. In the abbreviated nomen￾clature, a double-headed arrow connects the symbols specifying the anomeric carbons and their configura￾tions. For example, the abbreviated name of sucrose is either Glc(
1mn2)Fru or Fru(2mn1
)Glc. Sucrose is a major intermediate product of photosynthesis; in many plants it is the principal form in which sugar is transported from the leaves to other parts of the plant body. Trehalose, Glc(
1mn1
)Glc (Fig. 7–12)—a disac￾charide of D-glucose that, like sucrose, is a nonreducing sugar—is a major constituent of the circulating fluid (hemolymph) of insects, serving as an energy-storage compound. 246 Part I Structure and Catalysis Sucrose 4 5 1 2 H HOCH2 H HO HO 3 5 6 4 1 2 H OH OH H H CH2OH O H H O 6 Trehalose 3 5 1 4 2 H OH OH H O H OH HO 3 5 6 4 1 2 H OH OH H H CH2OH O H H H H O 6 -D-glucopyranosyl -D-glucopyranoside O OH H CH2OH 3 Glc( 1nn1 )Glc -D-glucopyranosyl - D-fructofuranoside Lactose ( form) 3 5 4 1 2 H OH OH H CH2OH O H HO OH 3 5 6 4 1 2 H OH OH H H CH2OH O H H H H O 6 -D-galactopyranosyl-(1n4)--D-glucopyranose Gal(1n4)Glc HOCH2 Glc(1nn 2)Fru FIGURE 7–12 Some common disaccharides. Like maltose in Figure 7–11, these are shown as Haworth perspectives. The common name, full systematic name, and abbreviation are given for each disaccharide. Abequose Abe Glucuronic acid GlcA Arabinose Ara Galactosamine GalN Fructose Fru Glucosamine GlcN Fucose Fuc N-Acetylgalactosamine GalNAc Galactose Gal N-Acetylglucosamine GlcNAc Glucose Glc Iduronic acid IdoA Mannose Man Muramic acid Mur Rhamnose Rha N-Acetylmuramic acid Mur2Ac Ribose Rib N-Acetylneuraminic acid Neu5Ac Xylose Xyl (a sialic acid) TABLE 7–1 Abbreviations for Common Monosaccharides and Some of Their Derivatives 8885d_c07_238-272 11/21/03 7:38 AM Page 246 Mac113 mac113:122_EDL: