A-Glycosidases

One of the most important differences between cellulose and starch is that animals can digest starch Because the glycosidic linkages m starch are a an animal s a glycosidase enzymes can catalyze then hydrolysis to glucose When more glucose is... 

Three classes of oral therapeutic agent are available for treating patients with diabetes mellitiis (NIDDM) the arylsulfonylureas (known simply as sulfonylureas), biguanides, and a-glycosidase inhibitors. Since 1977, only the sulfonylureas have been approved for use in the United States, although the other classes are used elsewhere. 

Shiga toxins and related toxins from E. coli No proteins ( ) 28S rRNA A/-glycosidase Cleavage of 28S rRNA Inhibition of protein synthesis... 

Fig. 2.—Possible Formation of an Enzyme-linked Acylal (—X = Carboxylate) from an Aldono-1,5-lactone at the Active Site of a / -Glycosidase (after Sinnot and Souchard ).

Nishio, T., Hakamata, W., Ogawa, M. et al. (2005) Investigations of a useful a-glycosidase for the enzymatic synthesis of rare sugar oligosaccharides. Journal of Applied Glycoscience, 52, 153-160. 

A typical multi-enzyme reaction, presented in diverse variations, comprises the combined use of a glycosidase and a glycosyltransferase. If they are applied in one pot, the glycosidase product is directly processed by... 

Beau has applied the DCC concept to a number of carbohydrate systems [13-16]. Carbohydrate-binding proteins often exhibit weak ligand interactions with millimolar dissociation constants, a quite different scenario to the enzyme-small molecule DCLs discussed thus far. The protein target initially chosen for study was hen egg-white lysozyme (HEWL), a glycosidase known to bind A-acetyl-o-glucosamine (d-G1cNAc) with... 

Recently McDonald et al. reported the synthesis of (1 —> 5)-linked D-mannoseptanosyl di- and trisaccharides.80 Once again they utilized differentially protected phenyl 1-thio-a-D-mannoseptanoside as donor and methyl a-D-mannoseptanoside as acceptor to synthesize the di- and tri-a-septanosides exclusively. The strategy used for their synthesis mirrored that depicted in Scheme 26. The septanoside structures and their properties in a glycosidase assay are presented in Section IV. 

A. Varrot, M. Schiilein, M. Pipelier, A. Vasella, and G. J. Davies, Lateral protonation of a glycosidase inhibitor. Structure of the Bacillus agaradhaerens Cel5A in complex with cellobiose-derived imidazole at 0.97 A resolution,./. Am. Chem. Soc., 121 (1999) 2621—2622. 

T. M. Gloster, J. P. Turkenburg, J. R. Potts, B. Henrissat, and G. J. Davies, Divergence of catalytic mechanism within a glycosidase family provides insight into evolution of carbohydrate metabolism by human gut flora, Chem. Biol., 15 (2008) 1058-1067. 

Large deviations from normal batch-to-batch glycosylation pattern is most likely caused by the presence of a glycosidase capable of enzymatic degradation of the carbohydrate side-chains. The likelihood of such eventualities may be minimized by carrying out downstream processing at low temperatures, and as quickly as possible. 

Nucleophilic fluoroalkylation in the anomeric position has been performed with trifluorochloroethylene, or with perfluorovinyl ethers." The compound obtained with trifluorochloroethylene is an irreversible inhibitor of a-glycosidases (Figure 6.44). " Trifluoromethylzinc bromide can be used to perform the difluor-omethylation of hydroxyls in various positions, probably through a carbenic mechanism. 

Figure 7.28 Cleavage of the glycosidic bond by a glycosidase with inversion of configuration. Inhibition by 5-fluoroglycosyl fluoride. ...

Meanwhile, the biological activities of the isolated compounds were studied extensively. Some were found to have obvious biological activities. For example, cardiac glycosides showed obvious anti-cancer activity and bartogenic acid can inhibit the activity of a-glycosidase and amylase... 

The intracellular distribution of a glycosidase in a mammalian tissue can be studied by centrifugal fractionation of a homogenate made in isotonic (0.25 M) sucrose solution. The membranes of subcellular particles are preserved in this medium and, provided that there is no leakage of the enzyme, its partition between the different sizes of particle can be measured. Before the enzyme is assayed, it may be necessary to destroy the structure of the particles, in order to make the enzyme completely accessible to the substrate. 

Starch molecules are digested in the stomach by enzymes called a-glycosidases, which break down the polysaccharide chain and release individual glucose molecules. As is usually the case with enzyme-catalyzed reactions, a-glycosidases are... 

Quiros LM, Aguirrezabalaga I, Olano C et al (1998) Two glycosyltransferases and a glycosidase are involved in oleandomycin modification during its biosynthesis by Streptomyces antibioticus. Mol Microbiol 28 1177-1185... 

Diazeniumdiolate anions as leaving groups at the anomeric position of carbohydrates can act as prodrugs, releasing NO upon hydrolysis by a glycosidase.18... 

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