New year, New series!

 

Happy new year, my friends! I hope you are having a great new year so far! With the new year, comes a new series on Biochemisty for Life! I am planning to start a series called: The enzyme of the month. Every month, I will write a blog describing various enzymes and their contribution to the normal functioning of a biological system. Just as an introduction blog, I will like to describe what enzymes are. 

For starters, enzyme names end with the suffix “-ase.” For example, lipase, an enzyme that breaks down lipids (fats), DNA Polymerase, which has a major role in DNA replication, and topoisomerase, enzymes that bring about the winding and unwinding of the DNA. The enzymes mentioned here end with the suffix “ase.” Biologists are very serious about naming their beloved macromolecule. Why are these enzymes so important? The answer lies in the fact that enzymes are biological catalysts. Without these enzymes, carrying out the metabolic processes in the body would become difficult because of the high activation energy. Enzymes, thus, lower the activation energy of a particular chemical reaction. There are various methods that enzymes apply for lowering the activation energy. One of these methods is changing the conformation of the reactants. Because structure defines function in biology, a small conformational change in the reactants can help with initiating the chemical reaction. You must be wondering, why on Earth we require enzymes for lowering the activation energy in the biological systems? Without the ability to lower the activation energy, the chemical reactions in living organisms would be a problem. In biological systems, high activation energy can be unsuitable, especially, because the energy is in the form of heat. High temperature can lead to a change in structure, and as mentioned earlier, structure defines function in biology. A slight structural change can lead to damage to the function. 

            Let us now explore the structure of the enzyme. Enzymes are proteins which means their structure comprises amino acids. The site where the enzymes bind to their substrates (reactants) is referred to as an active site. These active sites are very particular about what substrates they bind to. Therefore, an enzyme has a specific role in a biological system. Two models describe the enzyme-substrate binding:

          A. Lock and Key model: The enzyme and substrate binding is perfect. There is no conformational change observed in the enzyme for the substrate to bind to the active site. 

         B.  Induced Fit model: The enzyme has to undergo a slight structural change for the substrate to bind to the active site¹.  (Please refer to the image below)  

Image Citation link

Image Citation Link

            There are many natural factors that regulate the activity of the enzymes including pH, temperature, substrate saturation, and enzyme concentration. All the enzymes have a typical pH and temperature range where they optimally perform their tasks. If the enzyme experiences changes in the pH or temperature, the structure of the enzyme, and its function can be compromised. Moreover, if there are more substrates than the enzymes, the rate of the reactions lower than the normal. The body, therefore, has a system that “communicates” the imbalance in the ratio between substrates and enzymes to the nucleus to induce gene expression. Cellular communication is a rather complex topic that is a discussion for the other day! These are natural factors that can affect the reaction rates carried out by the enzymes. 

            There can be competitive and noncompetitive inhibition that can affect the rate of the enzymes. Competitive inhibitors² bind to the active site of the enzymes and “compete” with the substrates of the enzymes. The binding of the inhibitors can cause a conformational change in the active sites which has the ability to permanently block the enzyme activity. Whereas non-competitive substrates bind to the allosteric site ³ of the enzymes that temporarily blocks the enzyme activity. This allows for saving the energy of the cells when the enzyme activity is not needed. 

           On an ending note on this introductory blog, I would like to mention that I absolutely respect the value of enzymes. With this new year series, I hope to cultivate this respect for the enzymes within my readers. Please stay tuned for more enzyme related blogs! 

 

 

Footnotes:

1.     1.  Even though structure defines function in biology, this slight conformational change is needed for the enzymes to carry out their tasks.

2.     2.  An example of competitive inhibitors is cyanide which blocks the enzymes participating in cellular respiration. Hence, the cells cannot produce energy leading to dangerous consequences.

3.     3.  A binding site that is different than an active site on an enzyme. A substrate that induces or inhibits the enzyme activity binds to this site to regulate the activity of the enzyme.

Works Cited:

 

Enzymes - an overview | ScienceDirect Topics. (2011). Sciencedirect.com. https://www.sciencedirect.com/topics/neuroscience/enzymes

6.2D: Activation Energy. (2018, July 10). Biology LibreTexts. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/6%3A_Metabolism/6.2%3A_Potential_Kinetic_Free_and_Activation_Energy/6.2D%3A_Activation_Energy