Glycosidic Bonds in Sucrose

Configuration of the Glycosidic Bonds in Sucrose 1. Proof of the a-io-Glucopyranoside Configuration 

The researches of Hudson, together with those of Dubrunfaut, Tanret, Lowry and others, which he reviewed, clearly established the 

—Decrease with time in specific rotation at 0° of approximately 5% sucrose solutions completely and quickly inverted by invertase. Plot II corresponds to a somewhat higher acidityj than plot I. 

The result, [a] D -f-110° with an error of not more than + 2°, showed that prior to mutarotation the D-glucose was the ordinary a-form of rotation approximately - -109°, now known as a-D-glucopyranose. Sucrose, then, was an a-D-glucoside. Inspection of Fig. 1 also shows that after inversion but before mutarotation the sum of the rotations contributed by the a-D-glucose and the D-fructose remained very close to the specific rotation of 66° possessed by the original sucrose. The relationship  

Comparisons made with the same invertase solutions showed that the methyl and benzyl / -D-fructofuranosides were hydrolyzed 13.5 and times, respectively, more slowly than sucrose, and that the rates 

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Hestrin and his co-workers succeeded in Uberating the enzyme (levansucrase) from washed cells of A. levanicum by autolysis in the presence of thymol and chloroform, and showed that it converts sucrose to levan and glucose. In this reaction a 2,6-linkage is substituted for the glycosidic bond in sucrose, forming the levan ... 

Ethanol production from sugarcane (Saccharum sp.) is one of the easiest and most efficient processes since sugarcane contains about 15% sucrose. The glycosidic bond in the disaccharide can be broken down into two sugar units, which are free... 

Pancreatic (a) amylase is an endoglycosidase, which removes maltose units from amylose or amylopectin. It splits the a-1,4 glycoside bond. In the absence of an a-1,6 glycosidase, limit dextrin is a product in addition to maltose. Sucrose is nonreducing lactose is reducing. 

Enzymatic rearrangement of sucrose with Protoaminobacter rubrum CBS 574.77 performed on an industrial scale, affords isomaltulose (also named palatinose ) widely applied as artificial sweetener. Interesting optically pure derivatives (e.g. spiro-system f or analogs of nojirimycin 4) were obtained by hydrolysis of the glycosidic bond in functionalized sucroses. Sucralose (l, 4,6 -trideo)gr-l, 4,6 -trichloro-gaZarto-sucrose), prepared by chlorination of 6-0-acetylsucrose with S02Cl2/pyridine, represents an example in which the disaccharide skeleton is only slightly modified. 

Sucrose can be split hydrolytically by a glycosidase known as saccharase or invertase. Invertase, because as a result if its action the plane of polarization of polarized light is inverted sucrose is dextrorotatory (+). In the hydrolysate the highly laevorotatory (—) fructose outweights the more weakly dextrorotatory glucose so that overall a laevorotation results. More chemically expressed, invertase is a j8-fructofuranosidase since it is in the form of a j8-fructofuranose that fructose takes part in the glycosidic bond of sucrose and the enzyme cleaves this bond on the side of fructose. 

In the hydrolysis of the disaccharide sucrose by the enzyme sucrase, a molecule of sucrose binds to the active site of sucrase. In this ES complex, the glycosidic bond of sucrose is in a position that is favorable for hydrolysis, which is the splitting by water of a large molecule into smaller parts. The R groups on the amino acids in the active site then catalyze the hydrolysis of sucrose, which produces the monosaccharides glucose and fructose. Because the structures of the products are no longer attracted to the active site, they are released, which allows sucrase to react with another sucrose molecule. 

The most familiar of all the carbohydrates is sucrose—common table sugar. Sucrose is a disacchar ide in which D-glucose and D-fructose are joined at then anomeric carbons by a glycosidic bond (Figure 25.7). Its chemical composition is the same ine-spective of its source sucrose from cane and sucrose from sugar beets are chemically identical. Because sucrose does not have a free anomeric hydroxyl group, it does not undergo mutarotation. 

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