FERMENTS AND FERMENTATION. - Ferments or enzymes are catalysts produced by living organisms that perform their work in the metabolism (v. FISIOLOGIA) of living beings.
Like all catalysts, they do not shift the state of equilibrium of a chemical system, but they modify the rate at which that equilibrium is reached; in other words, they accelerate (or retard) the rate of chemical reactions, and they are not destroyed in the catalyzed reactions.
From the chemical point of view, f. are protein substances, and often it is possible to distinguish in them a chemical group, particularly important in the function of the f., which takes the name of coferment; many vitamins, such as the vitamins of the B group, enter into the composition of coferments.
Most f. act within the cell itself, from which they can be more or less easily detached, but some f. are secreted by the cell to act outside it, albeit for the benefit of the organism. To the latter belong those very well-known ones that break down food substances in the digestive tract (digestion) and that are released in the oral cavity (ptyalin), in the stomach (pepsin, chymosin) and in the intestine (trypsin, steapsin, amylopsin, etc.).
F. make possible the hydrolytic and oxidative degradation of the food fuel, which otherwise, at the temperature of living organisms, could occur only with extreme slowness; they moreover regulate this degradation so that the release of energy occurs in an orderly manner according to need and not tumultuously.
Enzymes are usually classified according to the reactions they catalyze; thus two great categories are distinguished: 1) hydrolases, or hydrolytic enzymes, which catalyze the reactions that bring about the breaking of a complex molecule into simpler ones with the uptake of a molecule of water, such as the splitting of sucrose into glucose and fructose. 2) desmolases, or desmolytic enzymes, which serve to accelerate the breaking of the simpler molecules that result from hydrolysis, and the complete oxidation of organic substances to water and carbon dioxide. Very important in this category of enzymes are precisely the oxidases and the dehydrogenases, oxidizing f.
The mechanism of action of f. consists in decreasing (or increasing) the chemical inertia of the fermented substrate by means not always fully known, but which in general lead to the formation of intermediate compounds between substrate and enzyme.
Bibliography
Vittorio Capraro