Page:Popular Science Monthly Volume 73.djvu/85

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HE question of enzymes is one of fascinating interest to the biologist. There is more or less of a mystical atmosphere surrounding these unknown ever-present bodies in all living organisms, on account of the difficulty in effecting their isolation, and in regard to the method in which they perform their function. The study of enzymes has been pursued with much vigor for years by eminent investigators of the biological sciences, and yet their exact nature is almost as little understood to-day as ever. No enzyme has been absolutely isolated, and consequently the chemical constitution of these principles is yet a matter of conjecture. We can, however, unerringly detect their presence, both qualitatively and quantitatively.

The terms enzyme and ferment as used to-day are practically synonymous. The latter term is doubtless the more familiar of the two to the laity. A classical example of fermentation is the changing of sugar, by means of yeast, to alcohol and carbonic acid gas. The yeast is necessary to this process, in so far as it elaborates the active agent—enzyme, or ferment—which is essential. The yeast, more properly according to our former conception, than now, is spoken of as an organized ferment. This was on account of the supposition that the yeast itself was the ferment. It has only recently been shown that a substance can be extracted from the yeast cell, which brings about the process, spoken of as fermentation. In contradistinction to the organized ferments there were the unorganized ferments, as, for example, the enzymes of the alimentary canal, which were capable of bringing about digestion as w T ell outside of the body in a test beaker, as in their normal habitat, the stomach and intestines. The separation of a material from the yeast cell, which still possessed its activity made obsolete the classification of unorganized and organized ferments. The agents which were formerly classified under the two heads, although differing in characteristics, are alike in that both are definite chemical substances secreted or manufactured by cells—a single-celled organism in one case and a multicellular in the other. Many bacteria were formerly believed to belong to the same class as the yeast, and thought to possess a fermentative function; now it is known that the bacteria elaborate a substance which has the enzymotic properties.

The physiologist defines an enzyme as a body, which, remaining