Enzymatic catalysis

It is very difficult to give an exact date for the discovery of enzymes. Activity outside a living cell was observed in 1783, when Spallanzani noted that meat was "liquefied" by the gastric juices of falcons.

Similar observations were subsequently made, but the first discovery of an enzyme is generally credited to Payen and Persoz, who in 1833 treated an aqueous extract of malt with ethanol, precipitating a heat-labile substance that initiates starch hydrolysis. They called this fraction "diastase". Today, we know that diastase was an impure preparation of amylase.

The word enzyme, Greek for "in yeast", first appeared in 1878: Kühne used it to distinguish between "organized ferments" (the whole micro-organism) and "inorganized ferments" (excreted by micro-organisms).

It was in 1897 that Bertrand observed that some enzymes required dialyzable factors for catalytic activity: these substances were called coenzymes.

From the early 20th century onwards, numerous attempts were made to purify enzymes and describe their catalytic activity in precise mathematical terms.

In 1902, Henri suggested that an enzyme-substrate complex was an obligatory intermediate in the catalytic reaction. He also gave a mathematical equation that took into account the effect of substrate concentration on reaction rate.

The effect of pH on enzyme activity was first demonstrated by Sorensen in 1909, and it was in 1913 that Michaelis and Menten rediscovered Henri's equation. This equation is based on simple principles of chemical equilibrium.

The fact that enzymes are proteins was not accepted until the late 1920s.

Finally, in 1965, Monod, Wyman and Changeux presented a kinetic model for allosteric enzymes (regulatory enzymes...