In 1877, German physiologist Wilhelm Kühne (1837–1900) first used the term enzyme, which comes from Greek, "in leaven", to describe this process. An enzyme is a protein produced by living cells for the purpose of regulating metabolic, biochemical reactions in living organisms. It is comprised of specially folded globular proteins and a co-enzyme (or cofactor). The beauty of an enzyme is not only the increased reaction rate it provides, but also its uncanny ability to remain undestroyed by the reaction itself. This property, credited to the coenzyme, allows it to deliver its benefits over and over again.

Enzymatic reactions
In enzymatic reactions, the molecules at the beginning of the process are called substrates, and they are converted into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at significant rates. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. Functionality of all enzymes is the same. That is the: “lock and key” model. Enzymes are very specific, and it was suggested by the Nobel laureate organic chemist Emil Fischer in 1894 that this was because both the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another. This is often referred to as "the lock and key" model. However, while this model explains enzyme specificity, it fails to explain the stabilization of the transition state that enzymes achieve.

Enzymes work as catalyst to conduct reaction
Like all catalysts, enzymes work by lowering the activation energy (Ea‡) for a reaction, thus dramatically increasing the rate of the reaction. Activation energy is the energy which is needed to conduct the reaction. Enzyme lowers the activation energy of the reaction and thus tends to change the path of the reaction.  By this way the enzyme increases the conversion rate of substrate to product in faster rate and in lower energy as shown in the figure below. As a result, products are formed faster and reactions reach their equilibrium state more rapidly. Most enzyme reaction rates are millions of times faster than those of comparable un-catalyzed reactions.                                        

They are almost invisible molecules, which are contained in the food we eat and are produced by our bodies. Scientists believe there are thousands of different enzymes, many of which have yet to be discovered. However, we can divide enzymes into three primary categories: metabolic, digestive and food. Metabolic enzymes are those enzymes that catalyze various chemical reactions within the cells such as detoxification and energy production. Digestive enzymes are secreted along the gastrointestinal tract to break down food so the nutrients can be absorbed into the bloodstream. Food enzymes are naturally present in all raw foods, providing an exogenous source of digestive enzymes when consumed. Not just in humans, in plants also the enzymes play equally important part. And for human consumption, some enzymes are plant originated as we humans eat several plant products. In short, to carry out biological processes, enzymes are the most important thing as without it the reaction won’t be completed. We can say that without enzymes, no biological processes are possible. There are certain factors that affect the activity of the enzyme such as, enzyme concentration, substrate concentration, temperature, pH and some other factors. But these days these factors are controlled and the maximum functionality is used.

Enzymes use as tools
The enzymes are broadly used as tools in agriculture, industries and medicine area. Let’s see some of the different enzymes and their applications in different fields. Development of medical applications for enzymes has been at least as extensive as those for industrial applications, reflecting the magnitude of the potential rewards: for example, pancreatic enzymes have been in use since the nineteenth century for the treatment of digestive disorders and potential of asparaginase for the treatment of lymphocytic leukaemia is promising. The variety of enzymes and their potential therapeutic applications are considerable. A selection of those enzymes which have realised this potential to become important therapeutic agents is shown in table below.

Therapeutic applications of enzymes



It is hard to corral the industry of enzymes. As catalysts, enzymes ubiquitously speed up chemical reactions on every imaginable front.

Not just in high-profile industrial or medical application, but enzymes are also used in everyday life, such as cloth washing, lowering the hardness of the water, lowering the alkalinity of the water, etc. Nothing can ultimately compete with enzymes from efficiency, cost and safety perspective. Definitely it makes enzymes - the smallest biological super hero.