Cellulose cellobiose from

Fig. 5. Modular nature of cellulolytic proteins. The enzyme illustrated (cellobiohydrolase) binds to the cellulose microfibril through the cellulose binding domain while the catalytic domain binds a single cellulose chain at a free end. Arrows representing the active site within the catalytic domain show the ability of cellobiohydrolase to remain bound to the substrate while the hydrolyzed product, cellobiose, is released. This allows the enzyme to progressively hydrolyze cellobiose from cellulose...

When faced with characterizing the kinetic behavior of an enzyme or a complex of enzymes, one usually pulls out a textbook on Michaelis-Menten kinetics and applies it to the system at hand. For beta-glucosidase, which hydrolyzes the soluble substrate cellobiose to glucose, this approach is fine. Unfortunately, for cellulase enzymes producing cellobiose from cellulose, this exercise is inadequate. 

Cellulases enzymes which hydrolyse cellulose to cellobiose, and which are found in plants, bacteria and fungi, TTie C. of Penicillium notatum is well-studied it consists of 324 amino acid residues (M, 35,000) with a disulfide bridge and no free SH groups. C. are used in digestion tablets, to remove undesired cellulose in foods, and for the preparation of cellobiose from cellulose. 

Besides the many known naturally occurring free oligosaccharides, a great variety of this class of compound can be obtained by enzymic degradation or controlled hydrolysis of a polysaccharide with acid. As an example, the treatment of starch with amylases produces maltose under certain conditions of acid hydrolysis, isomaltose can be obtained from starch, and cellobiose from cellulose. 

The most common naturally occurring disaccharides are sucrose (table sugar) and lactose (milk sugar). While sucrose is derived from plants and is prepared commercially from sugar cane and sugar beet, lactose is found in the milk of animals. Other common disaccharides that are produced by breaking down polysaccharides include maltose (obtained from starch) and cellobiose (obtained from cellulose). 

We have spent some time investigating possible heterogeneity in the Ci components of F. solani, T. koningii, and P. funiculosum. This has been done by testing for both Ci activity (defined as the enzyme that acts in synergism with the Cx enzymes to solubilize cotton cellulose or other crystalline cellulose) and cellobiohydrolase (release of cellobiose from H3P04-swollen cellulose) during different fractionation studies on the various Ci components. 

Figure 7. Production of glucose and cellobiose from Avicel. The reaction mixture contained 1% Avicel PH-101, 1% Trichoderma reesei QM 9123 cellulose protein produced in a pH 3.6 culture medium, and 0.05M sodium acetate buffer, pH 5.0. Incubation conditions and analysis are...

The CBH I (D) is identical in composition and activity to the CBH I (D) previously described (2) from T. reesei QM 9123. The close correspondence of their amino acid contents (Table VI), the nearly identical content of neutral carbohydrate 6.8% by weight for the CBH I (D) produced in the presence of sophorose and 6.7% for T. reesei QM 9123 CBH I (D) grown on cellulose (2), and identical electrophoretic properties clearly argue for a common molecular structure for these CBH s I (D). The CBH II is clearly different from all other CBH s in electrophoretic mobility (Figure 12) and amino acid composition (41), but is devoid of endoglucanase activity and produces predominantly cellobiose (>90% by weight of soluble products) from cellulose. It has a sedimentation coefficient of 3.71 in comparison to CBH I (D), for which a value of 3.66 was obtained. 

Hydrolysis of 1,4-linkages in 1,4-/3-D-glucans, to remove successive glucose units Hydrolysis of l,4-/3-D-glucosidic linkages in cellulose and cellotetraose, releasing cellobiose from the nonreducing ends of the chains... 

In the earlier literature, jS-D-glucose (3) was considered to be an intermediate compound which, on subsequent dehydration, provides levoglucosan. Experimental evidence against this theory has been adduced by Golova and associates, who obtained small yields of levoglucosan from jS-D-glucose and from cellobiose, as compared to a 54—60% yield from cellulose. 

Carbon monoxide, evolution from cellulose on beating, 428, 429 Carbonylation, of alkyl balides, 61 Carbonyl groups, formation from cellulose on heating, 426, 428, 435 Carboxyl groups, formation from cellulose on beating, 426, 427, 435 Cardenolides, synthesis of 1,2-cis-, 267 Cellobiose, /8-, mutarotation of, 23 Cellulase, 376 Cellulose... 

Exoglucanases, p-l,4-cellobiosidases, exocellobiohydrolases or p-l,4-cellobiohy-drolases (E. C. 3.2.1.91) hydrolyze p-l,4-D-glycosidic linkages in cellulose and cellote-traose, releasing cellobiose from the non-reducing end of the chain. 

Pilnik al (7) have noted that the combined action of pecti-nases and C-1 (1,4-p-D-glucan cellobiohydrolase, E.C. 3.2.1.91) enriched cellulases are able to almost completely liquefy pulped fruits and vegetables. For the actual dissolution of the cristal-line cellulose fibrils the C-1 enzyme is necessary which splits off cellobiose from the non-reducing end of the 1,4-p-D-glucan and which needs some C-x (1,4-p-D-glucan-glucanohydrolase, E.C. 3.2.1.4) to create such points of attack. Preparations rich in C-1 activity are usually obtained from Trichoderma spp. (8). 

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