Glycosides enzymic hydrolysis

The implications of the above observations may be important, especially if similar trends are observed in pyranose anomers. For example, with respect to the mechanism of acid-catalyzed hydrolysis of pyranosides, endocyclic C-0 bond cleavage (preceeded by 05 protonation) may be assisted in P-anomers in which the Cl-01 bond is equatorial, since the 04-Cl bond may already be extended in these anomers. By a similar argument, exocyclic C-0 scission (preceeded by 01 protonation) may be assisted in the hydrolysis of a-pyranosides in which the Cl-01 is axial and extended, thus resembling the transition state. Post and Karplus have recently suggested that enzyme-catalyzed glycoside hydrolysis of P-pyranosides may indeed take place by ring oxygen protonation, followed by endocyclic C-0 bond scission. 

The two canonical mechanisms of enzymatic glycoside hydrolysis were first proposed by Koshland in 1953. Since then, considerable amounts of structural and mechanistic data have been accumulated in support of the proposed mechanisms, both of which involve nucleophilic displacement steps. The reactions result in either net (1) inversion, or (2) retention of the substrate anomeric configuration." " " The following section provides an account of these two basic mechanistic groups of enzymes. 

Dennhart, N. and T. Letzel. 2006. Mass spectrometric real-time monitoring of enzymatic glycosidic hydrolysis, enzymatic inhibition and enzyme complexes. Anal. Bioanal. Chem. 386 689-698. 

Some informal data indicate that wines treated enzymically to hydrolyze glycosides were more intense and complex than control samples (Gunata et al. 1993). However, formal sensory panel studies are necessary to quantify and describe the characteristics that grape glycoside hydrolysis can contribute to varietal... 

Hydrolysis and other Reactions and Features.—A. novel method for following the add catafysed hydrolysis of sucrose and lactose involves measurement of the rate of reaction of periodate with quenched aliquot portions of the solutions using a periodate>sensitive electrode. In this way sucrose could be determined in the presence of other carbohydrates in the range 0.01-0.1 M, and the method was applied to food products. The glycosidic hydrolysis of fluorenone ketal (107), which serves as a nucleoside glycosylase enzyme model, has been shown to be intramolecularly catalysed by comparison with analogous compounds. ... 

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