Glycosidase enzymes

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... 

The Hanna group developed a rapid route to (+)-calystegine B2 (7-79) [35], a natural product with strong glycosidase enzyme-inhibiting properties [36]. As the key step, a triple domino procedure first published by Madsen and coworkers was em-... 

Trihydroxyazepanes (trideoxy-l,6-iminohexitols) have also been prepared from carbohydrate precursors and activities as inhibitors of selected glycosidase enzymes assessed... 

There is considerable interest in imino-sugars and analogues as glycosidase enzyme inhibitors. The synthesis of a "homonojiritriazole" derivative 35 has now been reported... 

Cycloaddition reaction of nitrone (—)-(394) with dimethyl maleate D14 has been used for the synthesis of two new polyhydroxyl pyrrolizidines (687) and (688) (Schemes 2.293, 2.294). These compounds are analogs of alkaloids ros-marinecine and crotanecine, which were assayed for their inhibitory activities toward 22 commercially available glycosidase enzymes. One of them ((-)- a-epi-crotanecine) (—)-(688) is a potent and selective inhibitor of a-mannosidases (310). The reaction of (—)-(394) with dimethyl maleate gave a 9.6 6 1 mixture of cycloadducts (—)-(680), (+ )-(680), and (—)-(681), which arise from anti-exo,... 

Highly-efficient general acid catalysis of acetal hydrolysis is involved in the reactions of glycosidase enzymes such as lysozyme (Dunn and Bruice, 1973)... 

Both alkaloids (castanospermine and swansonine) have the ahility to inhihit glycosidase enzymes (GE), the activity of which is necessary in glycoprotein biosynthesis. 

In the glycosidic form they are almost odorless, but once the sugar moiety has been cleaved (e.g., by action of glycosidase enzymes) they regain the aromatic characteristics (95AJEV187). Also synthesis of glycosides has been reported (95JAFC974). 

When a glycosidase enzyme cleaves an O-glycoside, we should expect a simple general acid-catalysed first step followed by fast addition of water to the intermediate oxonium ion, essentially the same mechanism as is shown by the chemical reaction (Chapter 13). 

An examination of hydrolysates produced by glycosidase enzyme or pH 3.2 acid treatment of reversed-phase isolates frcm juices of "non-floral " itis vinifera vars. Chardonnay, Sauvignon Blanc and Semilion demonstrated that these grapes contain conjugated forms of monoterpenes, C, norisoprenoids, and shikimic acid-derived metabolites. The volatile conpounds obtained hydrolytically from the conjugates were produced in sufficient concentration to permit ready analysis by GC/MS. The products of pH 3.2 hydrolysis have sensory significance when assessed in a neutral wine. The study further develops the precursor analysis approach as a technique to facilitate research into varietally specific constituents of grapes. 

Isotrehalose and neotrehalose are chemically similar to trehalose (Problems 25.58 and 25.591 except that neotrehalose is hydrolyzed only by /3-glycosidase enzymes, whereas isotrehalose is hydrolyzed by both a- ancl S-glycosidase enzymes. What are the structures of isotrehalose and neotrehalose ... 

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