Enzyme Structure: Definition and Examples

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What is Enzyme Structure?

Because the bonds of one sugar molecule contain a lot of energy, sugars like glucose are the foundation of all life on Earth. If you just poured this sugar into water and waited for it to dissolve, it would take thousands of years for all of the energy to be released.

When you ingest sugar, on the other hand, the energy from this molecule is available to your cells in just minutes! This is due to the fact that cells carry a secret weapon in the form of enzymes. Thousands of enzymes are produced by your body to not only break apart all sorts of macromolecules, but also to put them back together!

Enzymes are proteins that have a particular structure that allows them to combine or degrade substrate molecules. You should remain with us while we cover everything you need to know about Enzyme Structure and Properties of Enzymes, as this will most likely be on the AP test!

The vast majority of enzymes are essentially proteins with extremely precise structures, with the exception of a few RNA structures that may catalyse biological processes and serve as enzymes. Let’s take a short look at protein structure.

What is Protein Structure?

A chain of amino acids makes up all proteins. Ribosomes, link 20 distinct amino acids with unique characteristics to form huge chains. Primary structure refers to the chain of amino acids. The polypeptide naturally generates a secondary structure once the ribosome has connected the required amino acids in the correct order.

Interactions between neighbouring polypeptides generate structures like alpha-helices and beta-sheets, which are secondary structures. The protein now has to find the proper environment in which to fold into a more complicated tertiary structure.

Secondary motifs and individual amino acids interact in a complicated way to form this structure. Finally, when multiple separate polypeptide chains come together to form a much bigger protein structure, quaternary structure is generated. The active site is the sole real variation in enzyme structure.

A substrate molecule (or molecules) can bind to the active region inside the protein structure. When a substrate attaches to an enzyme, the enzyme slightly changes shape and exerts force on the substrate. This conformational shift has the potential to split apart a bigger molecule or to bring two smaller molecules together!

Secondary sites on certain enzymes allow chemicals like coenzymes to bind. These chemicals allow enzymes to be switched on and off, allowing the cell to precisely regulate when the enzyme can work.

Consider this… One of the things your doctor measures when you have a blood test is the number of different types of enzymes in your blood. Your doctor can deduce the many sorts of responses that are occurring within your body using this information.

Because enzymes are very specific to the molecules they work on, the presence of an enzyme in your circulation indicates that particular processes are occurring in your body. Some enzymes are associated with excellent health, while others might suggest that specific parts of your body aren’t functioning properly.

Consider how a doctor may utilise the characteristics of enzymes to anticipate what is happening in your body as we continue our study of enzymes. The catalytic property of enzymes is their most significant feature. Enzymes, in other words, can catalyse (or speed up) processes by decreasing the activation energy required to initiate them.

Most reactions take a lot of energy to get started without an enzyme. Because the enzyme changes form as it binds to the substrate, it adds a significant amount of energy to the substrate molecules. This drastically decreases the amount of energy required to initiate the reaction!

The reaction will proceed normally without the enzyme after it has been started. This indicates that the end products of an enzyme-catalyzed reaction have the same total energy change as if the reaction had not occurred. This catalytic feature allows cells to use various compounds at a far quicker pace than would be possible with basic chemistry.

In other words, the catalytic feature is what allows your body to access the energy available in glucose in minutes rather than the hundreds of years it would take for glucose to break down naturally.

Specificity is another characteristic of enzymes. To put it another way, enzymes are very selective to the substrates on which they are designed to function. If the incorrect molecule attempts to reach the active site, it will be denied. This indicates that an enzyme can only work with a single, highly particular sort of molecule as a substrate.

Enzyme specificity can also target a variety of features of a substrate molecule. The active site, for example, may contain a specific charge that allows it to bind exclusively to substrate molecules with opposing specific charges. Enzymes are notoriously picky, even rejecting isomers and enantiomers of the substrate they’re intended to operate with.

Only a certain substrate may create the enzyme-substrate-complex structure, trigger a conformational change in an enzyme, and acquire the energy required to conduct a specific reaction, thanks to enzyme specificity. This aids cells in ensuring that their enzymes do not conduct reactions across the cell at random.

The fact that all enzymes’ catalytic processes are reversible is one of their most significant characteristics. In other words, the same enzyme is frequently responsible for dissolving and reassembling two compounds, or vice versa. Consider how a certain catalytic protein usually breaks down a substrate into smaller monomers.

This enzyme may only function in one way under normal circumstances. The enzyme, on the other hand, may reverse its activity if the products accumulate on one side of the reaction. The enzyme would be combining two substrate molecules to form a single product molecule in this scenario.

This is critical for a variety of enzymes involved in energy generation in your body. For example, the enzyme “creatine kinase” is found in muscle and nerve cells and allows them to store massive amounts of energy that can be retrieved quickly. Creatine kinase deposits part of the phosphate groups onto creatine molecules, resulting in phosphocreatine and ADP molecules, when the cell has built up a significant reserve of ATP molecules.

This lowers the quantity of ATP in the cell and allows it to produce more. If a muscle cell need a large amount of ATP rapidly, creatine kinase simply reverses the process and turns phosphocreatine and ADP into ATP for the cell to use!

The final crucial feature of enzymes for cells is that they are temperature and pH sensitive. This implies they can only work when the solution’s temperature and acidity are precisely correct. If an enzyme is exposed to temperatures or pH levels outside of these parameters, it will denature.

Because an enzyme’s amino acid sequence has evolved to work in certain temperature and pH ranges, some enzymes can withstand high temperatures or low pH balances while others cannot.

For two reasons, this is critical for cells. For starters, because enzymes can only work at certain temperatures and pH levels, cells may more efficiently compartmentalise their catabolic and anabolic processes. Certain compartments (such as lysosomes) are kept very acidic, and the enzymes in these compartments can only function in this environment.

If the enzyme got into the cytosol, it would swiftly denature before it could start destroying the cell’s insides. Second, it indicates that cells and organisms must use energy to maintain their enzymes’ functionality by regulating their temperature and pH.

This is why cells have a variety of integral membrane proteins that regulate the flow of ions and chemicals into and out of various compartments on a continuous basis. Furthermore, virtually all creatures have behavioural and physiological systems for regulating their temperature in changing surroundings, such as sweating or seeking shade when the temperature becomes too high!

Enzyme Structure Citations
  • Human β-glucuronidase: structure, function, and application in enzyme replacement therapy. Rejuvenation Res . 2013 Oct;16(5):352-63.
  • Engineering enzyme microenvironments for enhanced biocatalysis. Chem Soc Rev . 2018 Jul 17;47(14):5177-5186.
  • A mechanistic view of enzyme evolution. Protein Sci . 2020 Aug;29(8):1724-1747.
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