Glucosides hydrolyzation

Hydro-quinol, 1-4-Di-hydroxy Benzene.—The third isomeric dihydroxy benzene, viz., the para compound, i-4-di-hydroxy benzene, is known as hydro-quino or hydro-quinone. The latter name is derived from its relation to quinone (p. 636) from which it is obtained on reduction and which it yields on oxidation. Both hydro-quinol and quinone derive their names from the fact that they are obtained by the oxidation of quinic acid, an acid derived from the alkaloid quinine. The phenol is found in various plants or may be obtained from them by the hydrolysis of glucosides present, e.g., arbutin, which is a glucoside hydrolyzing into glucose and hydro-quinol. 

Therefore, the conclusion from these studies was that p glucosides hydrolyze by a syn elimination mechanism [67] which is supported by the conclusion reached by Perrin and Nunez in their study of amidine hydrolysis [68]. This conclusion also conforms to Sinnott s principle of least nuclear motion theory [69]. 

The configuration of the glucoside linkage is different in the two, however. Structures [I] and [II], respectively, illustrate that the linkage is a /3-acetal-hydrolyzable to an equitorial hydroxide—in cellulose, and an a-acetal-hydrolyz-able to an axial hydroxide—in amylose, a starch ... 

Cellulose is the main component of the wood cell wall, typically 40—50% by weight of the dry wood. Pure cellulose is a polymer of glucose residues joined by 1,4-P-glucosidic bonds. The degree of polymerization (DP) is variable and may range from 700 to 10,000 DP or more. Wood cellulose is more resistant to dilute acid hydrolysis than hemiceUulose. X-ray diffraction indicates a partial crystalline stmcture for wood cellulose. The crystalline regions are more difficult to hydrolyze than the amorphous regions because removal of the easily hydrolyzed material has Htde effect on the diffraction pattern. 

It was of interest to determine whether glycosides of 6-deoxy-D-xylo-hex-5-enopyranose were susceptible to enzyme hydrolysis by / -glucosi-dase. Since aromatic glucosides are hydrolyzed by this enzyme at a much faster rate than aliphatic glycosides, phenyl 6-deoxy-/ -D-rt/Zo-hex-5-enopyranoside (18) was prepared (20). Phenyl / -D-glucopyranoside was converted to the 6-tosylate by selective esterification and then, by conventional procedures, transformed to phenyl 2,3,4-tri-0-acetyl-6-deoxy-... 

Levi, Hawkins and Hibbert6 have recently confirmed the structure for L. mesenteroides dextran proposed by Fowler, Buckland, Brauns and Hibbert.34 Completely methylated dextran in an over-all yield of 71% was obtained by three methylations with dimethyl sulfate and sodium hydroxide, followed by six modified Muskat methylations. The methylated dextran was hydrolyzed at 140° with methanolic hydrogen chloride, and the mixture of methylated glucosides, obtained in 95% yield, was quantitatively separated by fractional distillation. 2,3-Di-methyl-D-glucose was identified by means of the phenylhydrazide of the corresponding D-gluconic acid. 

Amylo-1 —> 6-glucosidase obtained by Cori and Larner218 from rabbit muscles, and R-enzyme isolated by Hobson, Whelan and Peat219 from potatoes and broad beans, are typical debranching enzymes, which will hydrolyze the 6 — 1-a-D-glucosidic linkage rather than the normal 4 —> 1-a-D linkage. These enzymes will therefore be particularly important in determinations of the fine structure of amylopectin, if they can be sufficiently well purified. 

C3 and C4 of the glucon is an absolute one. Phenyl a-D-glucoside, phenyl /J-D-mannoside (II), methyl /S-D-guloside (III), involving reversal of the addenda at Cl, at C2, at C3 and C4, respectively, are not appreciably hydrolyzed by almond emulsin.29 Phenyl /3-D-glucoside (I) and phenyl... 

The data given in Table V show not only that pancreatic amylase hydrolyzes unfractionated starch and a linear substrate at different rates but also that, for equivalent time intervals with the same concentration of pancreatic amylase, the relative concentrations of the products formed from these two substrates differ. In addition, Table VIM,M summarizes comparative data for the products of the hydrolyses of potato starch, of com amylose, and of waxy maize starch when equivalent numbers of glucosidic linkages of these substrates had been broken. 

The use of the enzyme system then known as invertin, which was extracted from beer yeast with water and precipitated from the aqueous solution, was available to Fischer when he began his classical studies of the enzymic hydrolysis of glucosides reported in 1894. The stage was also set by another enzyme known as emulsin, which Fischer purchased from E. Merck, Darmstadt, and which was known to hydrolyze several natural aromatic glucosides such as salicin, coniferin, arbutin, and the synthetic phenyl glucoside. These aryl glucosides were already known to not be cleaved by invertin. 

Emil Fischer developed a strong interest in the structural requirements for enzyme activity as the result of effects of changes in the structures of the a-and -methyl glucosides on their properties as substrates for the enzymes invertin and emulsin, which, as we have seen, he had shown to be a- and yS-glucosidases, respectively. As already mentioned, he was fascinated in 1895 by the fact that emulsin had no effect on either the a- or /2-methyl xylosides (33). In a 1912 publication with Karl Zach (34), he reported that -methyl 6-deoxyglucoside was hydrolyzed by emulsin and wrote ... 

Alpha-amylases (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) have conventionally been employed in starch liquefaction. Alpha-amylases hydrolyze the alpha-1,4-glucosidic linkages of the starch, producing maltodextrins. The alpha-amylases... 

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