J8-glucosidases

Alternatively, the diastereomeric mixture of aldol adducts undergoes lithium aluminum hydride reduction, primary alcohol silylation, and chromatographic separation to afford 291. Subsequent Mitsunobu inversion at C-3 to furnish the j -alcohol 292 followed by a depro-tective sequence and ring closure provides (+ )-castanospermine (293). This poly-hydroxylated indolizidine alkaloid isolated from Castanospermum australe and Alexa leipetala is a potent inhibitor of various a- and j8-glucosidases [98] (Scheme 68). 

Trehalose is a nonreducing disaccharide (C]2H220n) isolated from the poisonous mushroom Amanita muscaria. Treatment with an a-glucosidase converts trehalose to two molecules of glucose, but no reaction occurs when trehalose is treated with a j8-glucosidase. When trehalose is methylated by dimethyl sulfate in mild base and then hydrolyzed, the only product is 2,3,4,6-tetra-O-methylglucose. Propose a complete structure and systematic name for trehalose. 

The enzymatic glycosylation of steroid alkaloids by extracts from S. lacini-atum 337) as well as in the potato tuber 338) has been investigated. A fungal j8-glucosidase capable of hydrolyzing a-tomatine and demissine has been isolated and purified and its properties studied 339). 

Facts 2 and 3 demonstrate that one of the glucose residues of maltose is present in a hemiacetal form the other, therefore, must be present as a glucoside. The configuration of this glucosidic linkage can be inferred as a, because maltose is hydrolyzed by a-glucosidase enzymes and not by j8-glucosidase enzymes. 

Conjugates between polysaccharides (e.g. dextrans, starch, and dextrin) and proteins (e.g. lysozyme, chymotrypsin, j8-glucosidase, casein, and serum albumin) have been prepared with the aid of cyanogen bromide. Loss of enzymic activity was offset by increases in the thermal stability and the resistance to proteolytic digestion. Glutaminase-asparaginase from Acinetobacter has been... 

Fig. 102. Cross section through the trunk of a spruce at the boundary between phloem and xylem. (A) unstained, (B) stained for )8-glucosidase, (C) stained for lignin. j8-glucosidase activity is detectable in the rows of cells where lignification is beginning. About 9 rows inwards from the cambium, lignin formation is complete and -glucosidase activity is extinguished (from Freudenberg and Neish 1968).

G alactosida.se, /3-glucuronida.se, and j8-glucosidase were demonstrated in megakaryocytes and platelets, and have been comparatively studied among man, dog, rabbit, mouse, and rat (Monis and Wasserkrug, 1967). 

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