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Thus, an enzyme could be brought to use often without being exhausted.

Enzymes could be defined as catalysts found in living cells, constituted by protein substances, that help facilitate complex biochemical and metabolic reactions. As a virtue of being catalysts, enzymes do not directly participate in the biological reactions but aid their efficient occurrence. Thus, an enzyme could be brought to use often without being exhausted. A few examples are Protease (an enzyme that helps break down protein into its simpler components), Proteases (a class of enzymes that help break down proteins into their constituent amino acids) Lipase(an enzyme that helps break down fat into its simpler constituents), amylase(that breaks down starch into glucose to aid energy production in the digestion process) and Lactase(an enzyme that works on Lactose, a major constituent of milk and as a result, dairy products such as curd, cheese etc). Enzymes are formed when a certain number (which means, at least a thousand) of amino acids are linked together in chains with the help of amide or peptide bonds. Enzymes are commonly added in beverages, chocolates, bread, curd, pre-digested baby food, washing powders etc. to aid their efficient preparation and effect.

Enzymes are made up of several amino acids and hence are structured the same as proteins. The enzyme consists of an active site or a substrate binding site. This site is where the substrate get attached and the chemical reaction takes place. The enzyme can break a bigger molecule to simpler ones or vice versa. The enzyme also contains a site other than the substrate binding site called the allosteric site or inhibitor site. The inhibitor site is functional when the enzyme is in inactivated stage. If the inhibitor site is filled by inhibitor in the enzyme, the shape of the active site is changed and therefore does not allow any substrate to get attached to the active site and does not process any further reaction. Enzymes have what biologist Emil Fisher, in 1984, described as the lock and key structure model. Enzymes, according to Fisher, are shaped in a certain way whereas the corresponding structures, called substrates have a shape that can fit into the enzyme’s “active site” like a key does in a lock. This is also one of the reasons why enzymes are found to be so specific in their working. The lock and key model, proposed by Emil Fisher could be understood with the help of the following diagram: In 1958, another scientist by the name of Daniel Koshland proposed a theory that suggested the active sites of enzymes to be flexible and modifiable and hence, could be reshaped by interactions with the corresponding substrates. In certain cases, Koshland believed, the substrate might also modify its shape to fit the enzyme. This theory is known as the “Induced Fit Hypothesis”. This happens when enzymes such as glycosidases function. The mechanism of the working of the enzyme, as described above, could be understood by the following figure depicting the working of the Induced

The general equation that could describe the working of an enzyme through the enzyme-substrate reaction is as follows: Substrate + Enzyme = (Substrate-Enzyme) > (Product-Enzyme or Intermediate) = Product + Enzyme. The enzyme-substrate interaction can better be explained by a lock and key mechanism. The substrate is the key and the enzyme is the lock. Each substrate is specific to its enzyme, same as how every key is specific to its lock. For example, a lactose molecule will only bind to a lactase enzyme because it has the substrate binding site which is specific to the substrate also called as active site. After the substrate is bound to the enzyme, the reaction takes place where old bonds are broken and new bonds are formed, hence making a new molecule. This new molecule is the product. The reaction if taken place without an enzyme would consume high amount of activation energy, but with the presence of enzyme consumes relatively less energy. The classification of an enzyme, is done keeping in mind its function, that makes it liable to fit in one of the following six categories, all ending with the suffix “ase”-

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