ABSTRACT
Enzymes are proteins that are able to catalyze chemical reactions, not only in cells but also outside the cells in extracellular liquids (such as blood), and even in vitro, if given the appropriate conditions. Historically, in the 1890s E. Büchner (Nobel Prize 1907) was the rst to demonstrate the catalytic activity of enzymes in a cell extract, thus refuting Pasteur’s thesis that life processes such as fermentation can operate only within living cells, and implying that enzymes are molecules that can be extracted and characterized. Only in the 1920s was it proven by Sumner, Northrop, and Stanley (Nobel Prize 1946) that physiological catalysts were proteins, although catalytic activity had been proposed to
21.1 Active Site Concept .....................................................................................284 21.2 Specicity, Activity, and Turnover ..............................................................285 21.3 Thermodynamics and the Mechanism of Enzyme Reaction .......................286
