Advances in Enzymic Hydrolysis of Cellulose and Related by Elwyn T. Reese

By Elwyn T. Reese

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The extraneous materials in cotton and wood include a wide variety of organic substances that are soluble in such STRUCTURAL FEATURES OF CELLULOSE 27 neutral solvents as acetone, ether, alcohol benzene, and water. They include waxes, fats, essential and fixed oils, oleoresins, sterols, organic acids, soluble saccharides (gums), certain growth promoting substances such as vitamins, and proteinaceous substances that are believed to be the residue of the protoplast of the fiber. The water insoluble substances usually are deposited within the gross capillary structure of the fibers ; the water soluble materials, at least in part, are deposited in the fine capillary structure within the fiber walls.

Cellulose I I I and I V are formed by treatment with anhydrous ethylamine and certain high temperatures, respectively. e. smallest repeating three-dimensional unit within the crystalline regions. These dimensions are shown in Table 4 for the four crystal forms. TABLE 4. 9 A A A 90° Since it is essentially impossible to prepare celluloses I I , I I I , and IV without also altering the degree of crystallinity of the material, it is difficult to determine whether their modified susceptibility to enzymatic degradation is due to changes in the unit cell dimensions of the crystallites alone or also to differences in the amount of amorphous material present.

It is possible, although not necessarily likely, that this particular conformation and planar orientation of the glucose units is the one of best fit in the active site of the enzyme. It is also possible, but still more unlikely in terms of modern understanding of enzyme specificity, that the active site of the enzyme is designed in such a way that the cellulose chains on all sides of a crystallite are in a steric orientation equally ideal for complex formation and subsequent substrate cleavage.

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