Cellobiose emulsin

This osone was first prepared from cellobiose phenylosazone by the benzaldehyde method196 on hydrolysis by emulsin it gave D-glucosone and D-glucose. 

Problem 22.36 Cellobiose, isolated from the polysaccharide cellulose, has the same chemistry as maltose except that it is hydrolyzed by emulsin. Give the structure of this disaccharide. ... 

Maltose is hydrolyzed by the enzyme maltase (specific for a-glycosidic linkage) to two units of glucose, but for the hydrolysis of cellobiose the enzyme emulsin (specific for (3-glycosidic linkage) is necessary. While maltose is the building block of the polysaccharide starch, cellobiose is the building block of another polysaccharide, cellulose. 

In 1896, Fischer developed the phenylhydrazine test" for the detection of hydrolytic scission of disaccharides, especially by enzymes this depends on the fact that the phenylosazones of disaccharides are soluble in hot water, whereas those of the monosaccharides are not. Lactose is hydrolyzed by emulsin (1894) and by lactase it is not fermentable by yeast, and is unaffected by invertase (1894). An extract of the small intestine of horses and cattle, especially from young animals, hydrolyzes lactose (1896). The action of enzymes on lactose allowed it to be classified, along with cellobiose and maltose, with the normal (and not the y-type of) methyl glucoside (1914). In the discussion of maltose, the relationship of lactose to the /9-series will be mentioned later. 

Cellobiose and its /3-glycosides were hydrolyzed to glucose by emulsin. Cellobiosone and hydrocellobial were also cleaved by this enzyme. Extracts of AspergiUus niger and Kefir (a Caucasian micro-organism that ferments milk) hydrolyzed cellobiose yeast extract was inactive. 

Cellobiose differs from (-l-)-maltose in one respect it is hydrolyzed by the enzyme emulsin (from bitter almonds), not by maltase. Since emulsin is known to hydrolyze only jS-glucoside linkages, we can conclude that the structure of (+)-cellobiose dilfers from that of (+)-maltose in only one respect the D-glucose units... 

Cellulose is present in the pure state in the hairs of the cottonseed. Complete acid hydrolysis of cellulose by strong, concentrated mineral acids gives D-glucopyranose in quantitative amounts. Careful partial hydrolysis in the presence of acetic anhydride and sulphuric acid (acetolysis) gives molecules of cellobiose (4-D-glucopyranose-j3-D-glucopyranoside) and trisaccharides which can be hydrolysed by the enzyme emulsin. Hence, it... 

CELLOBIOSE, or cellose, a )S-glucose-glucoside obtained indirectly when the polysaccharide cellulose is acetylated and hydrolysed the yield shows that at least one-third of cellulose is composed of cellobiose units. Cellobiose is hydrolysed by acids, by emulsin, lactase, and the specific enz3nne, cdlobiase, but not by maltase. The end-products are two molecules of glucose. In its properties cellobiose resembles maltose, but is less sweet and less soluble. It is not attacked by maltase, and hence is assumed to be a 8-glucoside. 

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