Enzyme

An enzyme is a protein that acts as a catalyst (a substance that speeds up a chemical reaction) and speeds up chemical reactions in living things. The chemistry of life would not be possible without enzymes since they allow reactions in organisms to happen very quickly and therefore support life. Each enzyme is highly specific and will only work in one particular reaction.

Like a catalyst, an enzyme is not consumed or used up during a reaction. Since it is not changed or affected in any way by the process it helps create, an enzyme is immediately ready to be used again for the same purpose. Enzymes are essential to living things because without them, most of the chemical reactions that take place inside an organism would happen too slowly to keep it alive. Temperature is a key factor in a chemical reaction, and the temperature of most living cells is too low to allow the necessary reactions to take place quickly enough. With the proper enzyme, temperature no longer is a limiting factor. Since without the right enzyme, the reaction might occur so slowly that the cell would die. Although enzymes are catalysts, they are far from being typical—while a catalyst can be any type of simple substance, an enzyme is a complex protein. Further, it is by far the most efficient catalyst, since it can, at times, increase reaction rates by factors of 1,000,000 or more.

Since enzymes are complex proteins, they have their own unique three-dimensional shape. It is this shape that makes a particular enzyme act in a certain way. Their shape is the determining factor in how they will act because of the nature of a chemical reaction. A chemical reaction results in the formation of a new compound from existing ones. The mechanism of a chemical reaction involves either the breaking or the forming of a chemical bond (the link between its atoms). Whether breaking or forming bonds, energy is always necessary, and it is here that enzymes play their part. Enzymes either add energy to make something happen or reduce the energy required for something to happen. Either way, they are able to create a reaction that would not have occurred without the enzyme.

Since each enzyme has a unique shape, it will only "fit" or work for one particular reaction. This means the more reactions an organism needs, the greater the number of different enzymes required. For example, in the process called cellular respiration (in which food is broken down to release energy), approximately thirty chemical reactions take place, and each is controlled by its own enzyme. It is estimated that the typical animal cell (roughly one-billionth the size of a drop of water) contains about three thousand different enzymes, all of which are programmed to work in a certain chemical reaction.

ANSELME PAYEN

French chemist Anselme Payen (1795–1871) investigated the chemical reactions carried out by plants and discovered diastase, the first enzyme known to science. He also introduced the filtering properties of activated charcoal and discovered cellulose, a basic constituent of plant cells.

Anselme Payen was born in Paris, France, the son of a lawyer who turned to a career in industry and started up several chemical production factories. At the age of twenty, Payen was put in charge of his father's borax production plant. Borax is a crystalline mineral often found in salt lakes that is refined and used in metallurgy (metal-making) and to make soaps, glass, and pottery glazes, among other things. Payen discovered a method of preparing borax from boric acid which was readily available from Italy. Since his production costs for this method were so low, he was able to undersell his competitors, the Dutch, who had a monopoly on borax. Five years later he turned his attention to his company's production of sugar from sugar beets. Seeking a way to remove color impurities from beet sugar, he invented a method of using activated charcoal to filter out, or catch, large molecules. As a result of Payen's process, the filtering properties of charcoal have since been put to many uses, the most notable of which was their use in gas masks during wartime.

In 1833, Payen made another major discovery. That year he separated a substance from malt extract (grain that was germinating or starting to sprout) that seemed to be responsible for speeding up the conversion of starch into sugar. Further tests suggested to Payen that this substance acted as yeast did, meaning that it acted as a catalyst. A catalyst is a chemical that usually speeds up the rate of a chemical reaction, but is not itself affected, or changed, in any way. Payen named this new substance "diastase" from a Greek word meaning "to separate," since in many ways it separated the individual building blocks of starch into its individual components of sugar. To his delight, he found that diastase even worked when it was taken out of the original malt extract that produced it. Diastase, therefore, could be called an organic catalyst, or an enzyme, since an enzyme is a substance that acts as a catalyst in biological systems. Thus, diastase was the first enzyme to be produced in concentrated form. Ever since, enzymes that have been discovered have been named with the "-ase" suffix, the pattern started by Payen.

Payen was the first to isolate cellulose, a carbohydrate (a compound consisting of only carbon, hydrogen, and oxygen). While studying different types of wood, he obtained a substance that was definitely not starch but that nonetheless could be broken down into units of sugar as starch could. Because he obtained it from the cell walls of plants, he named it "cellulose." Once more, Payen established a naming system, and ever since carbohydrates always end with "-ose," like glucose and sucrose. Much later, cellulose went on to be used as the building block for many other products. Treated with acids and other additives, it was the main ingredient in the manufacture of guncotton (an explosive), celluloid (film), cellophane, and rayon, among others. By 1835 Payen abandoned business altogether and became professor of industrial and agricultural chemistry in Paris. He died in Paris during the Franco-Prussian War after refusing to leave the city as the Prussian army advanced.

Enzymes work at the cellular level and can be considered a cell's chemical regulator or system of control. The needs of a living cell are constantly changing as it strives to adjust to the ever-changing demands of its environment. Therefore, the cell needs the flexible system of control that enzymes provide. Another advantage of an enzyme is that the reactions that it stimulates are reversible if the cell wants the opposite reaction.

The synthesis, or the making, of an enzyme is controlled by a specific gene. Usually it is a hormone that switches on the gene, which, in turn, signals that a certain enzyme should be produced. Since enzyme production can be turned on, it can also be turned off. Both of these on/off mechanisms are natural and happen all the time, but certain forms of artificial "inhibitors" can turn off production permanently. Many poisons and some drugs have this effect, and can lead to death. For example, certain nerve gases as well as the poison cyanide permanently inhibit or stop the important enzyme that allows the body to use oxygen. This results in a quick death. Besides the natural enzymes in the bodies of organisms, enzymes are put to use everyday in the production of beer, wine, cheese, and bread. Without the proper enzymes contained in yeast cells, none of these important food products could be made.

[See alsoProtein ]