Enzyme Basics: Science and History - Antibiotics in Action

Enzyme Basics
Science and History

Enzymes are proteins that are catalysts. This means they speed up chemical reactions in living organisms, but they aren't consumed in those reactions. Here are some important things you should know about enzymes:

Enzymes are effective in minute amounts (often too small to be detected by ordinary chemical tests) because they are not used up in the reaction that they catalyze.

Enzymes are specific to the reactions they catalyze, that is, each enzyme only catalyzes one specific chemical reaction.

Enzymes do not affect the direction of the reaction but make the reaction reach equilibrium sooner.

The living cell is a “container” for a multitude of biochemical activities that are lumped under the word metabolism. Both synthesis and decomposition of molecules in a living system would normally proceed too slowly to be useful to metabolic survival. Hence, the presence and activity of enzymes are vital to the life-supporting activities of cellular metabolism. Enzymes make up a substantial portion of the total protein of the cell. A typical cell contains about 3000 different kinds of enzyme molecules and many copies of each kind. Some of these biochemical activities are the basis of cell reproduction, conversion of compounds for cellular energy, and the synthesis of specific compounds that can be used within the cell or are secreted for extracellular reactions. Within a cell, chemical reactions take place within a narrow temperature and pH range. This is possible because enzymes generally lower the activation energy of a reaction through a variety of mechanisms. Many advances in controlling bacterial diseases come from an understanding of how certain enzymes within the bacterial cell operate. Interfering with these enzymes interferes with vital metabolic functions within the bacterium. Conversely, changing the genetics of a bacterium alters the production of various secreted substances, some of which turn out to be useful antibiotics. Certain vitamins, some of which are produced by bacteria (as in our intestine), are proteins that work in conjunction with other enzymes. The vitamins are then called coenzymes.

Some of the earliest studies on inorganic catalysts were done by the Swedish chemist Jöns Jakob Berzelius in 1835. Even though the catalytic activity of enzymes as found in yeast (the word enzyme is ancient Greek for “in yeast”) had been used for centuries, it was not until 1926 that the first enzyme was obtained in pure form (crystalline). This was done by James B. Sumner of Cornell University. He later (1946) received the Nobel Prize for his work with the enzyme urease, extracted from the jack bean. Urease is an enzyme that catalyzes the conversion of urea to ammonia and carbon dioxide. Certain bacteria that convert urea to ammonia as part of the nitrogen cycle contain this enzyme.

The conversion of urea and water into ammonia and carbon
dioxide, one of many biochemical reactions catalyzed by
enzymes.

Your morning yogurt
was made by bacteria
and their enzymes.

Herders who made canteens from the stomachs of goats and sheep found that when they filled them with milk instead of water the milk soon clumped into cheese. The agent for this transformation is rennin, an enzyme produced in ruminant stomachs and unique to mammals. It is used for the decomposition of milk protein. These same stomachs contain both bacteria and protozoans that produce additional enzymes for the chemical decomposition of the cellulose found in the cell wall of plants such as grass that ruminants depend upon for a source of energy. The cellulose is first converted into its constituent sugars through enzyme activity; the sugars are then metabolized for energy.

Yogurt, an ancient food with modern popularity, is prepared through the action of enzymes produced by several bacteria, especially Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus acidophilus.
For more information, at other Web sites...

Jöns Jakob Berzelius — biography, part of Chemical Achievers from the Chemical Heritage Foundation.
The Nobel Prize in Chemistry 1946 — biographies of James B. Sumner and his co-recipients from the Nobel e-Museum.

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Your morning yogurt...: Courtesy United States Food and Drug Administration.

Copyright ©2002 The Chemical Heritage Foundation