Cellobiose glucosidase

Hydrolysis of delignified wheat straw up to 90% was obtained in 96 hours with the cellulase system produced in SSF with wheat straw. It took only 72 hours to obtain over 90% hydrolysis of wheat straw with cellulase system produced with SSF on Pro-cell (Table VII). It is interesting to note that the quantity of cellobiose in the hydrolysate obtained with the cellulase system produced on Pro-cell was higher than that of the cellulase system produced on wheat straw. This is consistent with the observation that cellulase system produced on Pro-cell had a lower ratio of FP cellulase )3-glucosidase (1 0.77) as compared to that produced on wheat straw (1 1.2). However, this cellulase system had a faster hydrolysis rate it took only 72 hours to obtain over 90% hydrolysis. This might be related to cotton hydrolyzing activity of this cellulase system (Table V). 

B. W. Sigurdskjold, B. Duus, and K. Bock, Hydrolysis of substrate analogues catalysed by P-D-glucosidase from Aspergillus niger. Part II Deoxy and deoxyhalo derivatives of cellobiose, Acta Chem. Scand., 45 (1991) 1032-1041. 

EGC and EGD (C. t.). While CBH I and EG I from Tr. r., showed very similar specificities, they could be differentiated by adding small amounts of cellobiose, a strongly competitive inhibitor of the cellobiohydrolase (Fig. 1). The cellotrioside allowed detection of EG III activities in the culture filtrate of Tr. r. in spite of other activities being present the addition of small amounts of gluconolactone effectively suppressed glucosidase activity. 

Exercise 20-12 Cellobiose differs from maltose only in its behavior to enzymatic hydrolysis. It is hydrolyzed by yeast /3-D-glucosidase. What is its structure ... 

There are two reasons for the measurable cellobiose concentration in the T. viride cellulase hydrolyzed syrups. The most likely is that T. viride has rather poor / -glucosidase activity so that cellobiose accumulates. Evidence of this is that additions of / -glucosidase to the T. viride cellulase improves its activity. A second reason is that the / -glucosidase enzyme is strongly glucose inhibited. Hence the rate of cellobiose hydrolysis slows down as the glucose concentration rises, allowing cellobiose to accumulate. 

Table VI presents a kinetic model for preferred growth of a microorganism on cellobiose (C2) but having an extracellular / -glucosidase (E2) that is glucose inhibited and in which the glucose uptake is repressed. This model readily fits the cellobiose data shown by the solid lines in Figure 9 (20).

Both major and minor protein components separated in this way were Ci types. This was established when it was found that either acted in synergism with a mixture of the Cx and / -glucosidase activities to the same extent in solubilizing cotton cellulose (Table II). Furthermore, both components were cellobiohydrolases in that they could degrade H3PO4 cellulose to cellobiose. 

The sequential and cooperative roles of the enzymes are shown in Figure 1. Endoglucanases, often called cellulases or carboxymethylcellu-lases, provide nonreducing chain ends from which the exoCBH s cleave cellobiosyl residues. The cellobiose, which is inhibitory to the depoly-merizing enzymes, is cleaved to glucose by the / -glucosidase. Since the product of one enzyme may become the substrate for another, enzyme purification is an essential prerequisite to any clear description of the system. 

Figure 6. Transglycosylation activity of /3-glucosidase. The reaction mixture initially contained 3% cellobiose, 0.0009% (3-glucosidase, and 0.05M sodium acetate buffer, pH 5 0. Incubation was carried out at 45°C in a reciprocating shaker. Each sample was boiled for five minutes and analyzed by HPLC (Gt = glucose, G2 = cellobiose, Gs = trisaccharides.)...

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