Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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enzyme

A class of complex organic substances that are capable of acting outside of living organisms and can accelerate or catalyze specific chemical transformations, such as the formation of bloom on leather, the tanning of leather (see: BATING ), and the modification of native starches in sizing processes.

The rate of an enzymatic reaction depends upon the temperature, pH, substrate concentration, and the presence of activators, co-enzymes, and enzyme inhibitors. The reactions of enzymes usually accelerate with an increase of temperature; however, since enzymes are proteins and are denatured at elevated temperatures, reaction rates increase only to the point where denaturation overcomes the accelerating effect of increasing temperature.

Enzymes exert their influence by combining with the substrate to form an enzyme-substrate complex, which then decomposes to give the products and release the enzyme for further action. Because of this, the rate at which enzyme products are formed depends both on the concentration of the enzyme-substrate complex and the rate of its decomposition. The formation of the complex depends on mass action between the enzyme and the substrate; therefore, taking a given quantity of an enzyme, the complex increases with the quantity sufficient to convert nearly all the enzyme into the complex. (72 , 195 , 306 , 363 )




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