ENZYME (Gr. aleavened”, any of the unorganized ferments, such as diastase, cytase, trypsin, etc., which induce fermentive changes in organic substances. It was formerly thought that these °unorganized* ferments might be essentially different in their action from the so called ferments, such as the yeasts, molds and bacteria; but it is now known that the fermentive action of the "organized* class is due chiefly, and perhaps wholly, to the enzymes that they secrete. The chemistry of the enzymes is very imperfectly understood. According to some authorities they act merely by catalysis, being capable of effecting the fer mentive change of indefinite quantities of the substances upon which they act, without being themselves used up, nor exhausted in any way. According to other authorities, they are gradu ally destroyed by their own activity, so that a definite mass of any given enzyme can produce only a definite (though surprisingly large) amount of fermentive transformation. See FERMENTATION.
Chemical ferments, elaborated in the cells of plants and animals and capable of bring ing about a peculiar series of biochemical reactions, which are produced without the inter vention of physical factors or mineral sub stances. Under some conditions they have the properties of facilitating chemical interchanges between certain bodies without entering into the composition of the different products that result. These enzymes, or ferments, zymases, or dias tases, as they are frequently called, play an im portant role in the digestive processes, as well as being of vital importance in the general life history of nearly all plants. A knowledge of enzymes dates back to very remote periods. In the beginning of the 16th century observations on the phenomena of digestion called attention to this class of bodies; but it remained for Du brunfaut and Pasteur to place the science of fermentation on a stable basis. Enzymes are for the most part soluble in water, being thrown out of solution by a large number of chemical sub stances, such as alcohol, tannic acid, etc. They usually lose their activity at a temperature above F. Most of them decompose hydrogen peroxide and they act largely in proportion to their quantity. With reference to their chemical
composition, it would appear that they belong to the proteid class. There is usually a large proportion of inorganic salts, particularly cal cium phosphate, in their composition. A few, however, do not contain nitrogen. Although closely related to proteids, they do not give pro teid color-reactions. As to their formation, it is considered by some that they are oxidation products of albuminoid substances, or zymogens. The transition of the zymogen into the ferment is termed zymogenesis. Destruction of enzymes is termed zymolysis. As to the manner of action of this interesting class of bodies, a vast variety of phenomena may be observed. They may bring about molecular changes either by hydra tion or by oxidation. They appear to occupy the position of intermediaries, as it were. Many theories are put forward in attempting to ex plain the action of enzymes; but as they pre sent many analogies to living protoplasm, explanation of the phenomena of their activities is almost as difficult as to explain the phenomena of life. Attempts have been made to classify the various enzymes, but any classification must be of a transitory character, since knowledge concerning this group of bodies is increasing daily. The classification of the soluble ferments suggested by Effront is shown below.
Those enzymes secreted by plants and ani mals in the course of their digestive processes, such as invertin, which breaks up cane-sugar into a mixture of glucose and fructose, diastase, which has an analogous action on starch, ptyalin, found in the saliva, which also acts on starch, pepsin and trypsin, which decompose proteids in the acid medium of the stomach and the alkaline medium of the intestines, respectively, are not difficult of isolation, while almost none of the intracellular enzymes, which perform a far more important function in the life of the animal or plant, have yet been isolated.
The enzymes have many applications in the arts. Consult Effront, 'Enzymes and Their Applications> (New York 1902) ; Greene, uble