What are enzymes?

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The term enzyme was first coined in 1877 and is derived from the Greek words En Zymen, which mean “in yeast” as reference to first enzymatic activities described in yeast, during alcoholic fermentation.

Enzymes are biological catalysts, meaning catalysts that are found in biological systems such as bacterial cells, plant cells and animal cells. As catalysts, enzymes are molecular components that speed up chemical reactions. Because enzymes are consumed at the beginning of a chemical reaction and regenerated at its end, they are listed in neither the reactants side nor the products side of a typical chemical equation. Instead, the name of the enzyme is typically written on top of the chemical equation’s arrow. The reactant of an enzyme-catalyzed reaction is called Substrate. Enzymes work by forming highly specific complexes the substrate, at a location in the enzyme called the active site.

Enzyme_mechanism

Enzymes distinguish themselves from traditional chemical catalysts (such as temperature, metals, acidic environments, etc.) in many ways. Firstly, enzymes are specific to the chemical reactions that they catalyze. Typically one enzyme only speeds one particular chemical reaction. The specificity of enzymes is so peculiar that the orientation of one single hydrogen atom in space (as seen in some stereoisomers) could make the difference between catalysis and non-catalysis. By contrast, the traditional catalyst hydrogen ions (H+) can catalyze a wide variety of reactions, with a wide variety of reactants. Secondly, enzymes often work under mild chemical conditions such as mild temperatures and mild pH. These conditions are more compatible with life than the extreme temperatures (sometimes as high as 100◦C) and extreme pH (pH as low as 1), required to speed traditional chemical reactions in a test tube. Finally, enzymes distinguish themselves from traditional catalysts by the fact they accelerate chemical reactions much more efficiently. Carbonic anhydrase, for instance, enhances the rate of its reaction ten million times (107). Urease (an enzyme that catalyzes the hydrolysis of urea) enhances the rate of its reaction an astonishing one hundred trillion times (1014)!


The vast majority of enzymes are proteins, meaning polymers of amino acids. Examples include catalase, lactase, DNA polymerase and alcohol dehydrogenase. Although not a rule, the name of an enzyme typically end with the suffix “ase”. A few enzyme are made of ribonucleic acids (RNA). These RNA-enzymes are called ribozymes. Peptidyl transferase 23S rRNA is an enzyme of an RNA-enzyme that is found in the ribosome and that participates in the translation of proteins.

It is believed that life as we know it would not have existed without enzymes.

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