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Fundamentals Of Enzyme


Many chemical reactions in the body of an organism are slow and could take days to complete. The body of an organism cannot survive under these conditions since some processes, such as the digestion process, require a quick reaction to provide energy to the body. Living organisms speed up these reactions by the use of enzymes. Almost all the metabolic processes in animal cells require the catalytic effects of enzymes. Enzymes are body proteins that act as catalysts to the body’s chemical reactions without altering the reaction process. The enzymes are not destroyed as they speed up the reaction process and can be reused over and over again. The substance acted upon by an enzyme is called the substrate, and the enzymes work to convert these substrates into different molecules called products. The substrate has a region called an active site, and the enzymes bind to these active sites (Cornish-Bowden 2012, p.131).

Lock And Key Hypothesis

Before an enzyme can catalyze a chemical process in the body, it must bind to a substrate. The enzymes are particular on the type of substrate and the reaction to speed up. For many years, scientists have made efforts to explain the specificity of the enzyme on the substrate to bind. One representation accepted globally is the lock and key model, Which proposes that the substrate and the enzyme are made of geometrical shapes that fit exactly into one another.

Induced Fit Hypothesis

The lock and key model, however, fails to explain the stabilization of the enzyme after binding, and scientists with a modification of the model known as the induced fit model. This model is based on the flexibility of an enzyme. Since the substrate is also a protein, the amino acids forming the “walls” of the active site are reshaped according to the shape of the enzyme. This process happens as the enzyme interacts with the substrate (Fersht 2017, p.115).

Factors Affecting Enzymes

The fact enzymes are proteins in nature makes them prone to some factors that affect proteins (Cornish-Bowden 2012, p.170). Temperature affects enzyme reactions in the sense that very high temperature denatures the structure of the enzyme. Low temperature slows down the rate of enzymic activity by deactivating the enzymes, and the reactions and enzymes work best at the optimum temperature. Enzyme concentration and substrate concentration have a direct effect on the rate of enzyme reaction. An increase in enzyme and substrate concentration results in an increase in the rate of reaction. Enzyme activators such as cofactors and coenzymes also increase the rate of enzyme reaction. Inhibitors, both the non-competitive inhibitors and the competitive inhibitors, have a negative effect on an enzymic reaction. Inhibitors bind to the active sites in a substrate.

Effects Of PH On Enzyme Activities

The acidity or alkalinity of a solution also affects enzymes. Some enzymes work best in acidic environments, while others work best in alkaline environments. For example, the pepsin enzyme has a pH optimum of 4-5, while the lipase enzyme in the pancreas has a pH optimum of 8. Some enzymes, like enzyme catalase, have their optimum pH at seven, meaning they work best in neutral environments (Fersht 2017, p.122). Despite the fact that the optimum pH value varies according to the enzyme’s environment, extremely low or high pH values result in the deactivation of an enzyme in the body.

Importance Of Enzymes

Enzymes are used by many vital body processes. First, the digestive system of every organism requires the actions of an enzyme to take place. For example, enzymes amylase and protease break down large molecules of starch and proteins, respectively, into maltose and peptides that can be absorbed by the small intestines. Enzymes also facilitate the process of metabolism. The enzymes also have a critical role in disease prevention. For instance, their involvement in homeostasis controls genetic diseases (Drauz 2012, p.66).


Cornish-Bowden, A. and Cornish-Bowden, A., 2012. Fundamentals of enzyme kinetics (Vol. 510). Weinheim, Germany: Wiley-Blackwell.
Drauz, K., 2012. Enzyme catalysis in organic synthesis: a comprehensive handbook. John Wiley & Sons.
Fersht, A., 2017. Structure and mechanism in protein science: A Guide to enzyme catalysis and protein folding (Vol. 9). World Scientific.



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