Enzymes Properties: Definition, Structure and Mechanism

Enzymes are very specific biomolecules. All metabolic processes of our body need enzymes to catalyze the reaction faster. In this article, we will be covering various Enzyme Properties, structure, and classification. Enzymes are naturally produced by living cells, unlike catalysts. The activity of the enzyme decreases considerably at high temperatures. Most of the enzymes are globular proteins while some molecules are RNA. Enzymes are larger than substrates. The enzymes are located in the protoplasm in the form of hydrophilic colloids.

Keyterms: Enzymes, Biomolecules, RNA, cells, catalysts, proteins,  protoplasm, hydrophilic colloids, globular proteins

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What are Enzymes?

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Enzymes are found in all tissues and fluids in the body. Catalysis of all reactions that take place in metabolic pathways is performed by intracellular enzymes. Enzymes in the plasma membrane regulate catalysis in cells in response to cellular signals, and enzymes in the circulatory system regulate blood clotting. Most critical life processes are based on the functions of enzymes.

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Enzyme Structure

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Enzymes are the linear chain of amino acids and then gives rise to a three-dimensional structure. The sequence of amino acids will specify the structure and in turn, identify the catalytic nature of the enzyme. When heated the enzyme gets denatured and loses its activity that is associated with temperature. 

Most of the enzymes are globular proteins but some are RNA molecules. Enzymes are larger than substrates. 

Enzyme Structure

Enzymes are generally named after the compound or class of compounds upon which they work. For example, the enzyme that catalyses the hydrolysis of maltose into glucose is named maltase. 12 22 11 6 12 6 Maltase Maltose Glucose C H O → 2 C H O Sometimes enzymes are also named after the reaction, where they are used. For example, the enzymes which catalyse the oxidation of one substrate with simultaneous reduction of another substrate are named oxidoreductase enzymes. The ending of the name of an enzyme is -ase. 

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Enzyme as Biocatalyst

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• Enzymes accelerate the reaction rate by reducing the transition time between substrate and product.
• Enzymes as catalysts control reaction specificity and ensure that only specified substrates bind to an enzyme’s active site resulting in product production. 
• As catalysts, enzymes take part in biochemical reactions without altering the state of the reaction.
• Enzymes also initiate the biochemical reactions by decreasing activation energy and increasing transition energy 

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Properties of Enzymes 

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Physical Properties

• Enzymes act as colloids or high molecular weight substance 
• At temperatures below the boiling point of water, enzymes are destroyed or inactivated
• Enzymes at 60 degrees celsius are inactivated when in a liquid medium. 
• Dried enzyme extracts may withstand temperatures ranging from 100 to 120 degrees Celsius, and even higher.
• Enzymes have a temperature range, usually between 25 and 45 degrees celsius. At 37 degrees celsius, the enzyme reaction is maximum and once the temperature reaches 60 it becomes inactive. 

Chemical Properties 

• Enzymes have a great capability of converting large amounts of substrate into substance. And a huge amount of compounds can be catalyzed by a small number of enzymes
• A specific enzyme can catalyze a specific reaction that is called enzyme specificity.
• Enzymes improve the reaction rate and stay unaffected during the reaction

General Properties 

• Enzymes initiate and speed up the reaction
• The enzyme’s activity is ph dependent
• Enzymes have the capacity to forward and reverse the reaction but do not decide the direction of the biochemical pathway
• An enzyme has a particular area on which the substrate interacts to produce the desired product
• Enzyme becomes unstable at varying ph, high heat and temperature
• Enzymes have protein like characteristics
• Substrates can be catalyzed with a small number of enzymes
• Enzyme activity represents absolute, relative, group and stereo specificities
• Some enzymes perform regulatory function
• Enzymes minimise activation energy
• The enzymes remain unaffected before and after the product formation and can be reused
• Enzymes are soluble both in water and NaCl

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Mechanism of Enzyme Action

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The mechanism of enzyme action is dependent on the parameters such as temperature, pH and concentration of enzyme and substrate. At an ideal temperature of 37 degrees celsius and pH of 7.2, the enzymes are most active. The enzymatic reaction will be slowed down by the small concentration of enzyme and substrate. 

Also, the high concentration of enzymes will speed up the enzyme activity. This is because more substrates will interact with the enzyme’s active site for the formation of a product. When the reaction activity reaches a maximum level, there will be no changes in the enzymatic reaction even after the addition of the enzyme and substrate.

Similar to the action of chemical catalysts, enzymes are said to reduce the magnitude of activation energy. For example, the activation energy for acid hydrolysis of sucrose is 6.22 kJ mol^–1, while the activation energy is only 2.15 kJ mol^–1 when hydrolysed by the enzyme, sucrase.

Mechanism of Enzymes

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Classification of Enzymes

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Enzymes are classified on the basis of the action it performs:

Classification of Enzymes

• Oxidoreductases- oxidation-reduction reactions
• Transferases- transfer of the functional group
• Hydrolases- hydrolysis reactions
• Isomerases- isomerization reaction
• Lyases- addition to double bonds
• Ligases- formation of bonds with ATP cleavage

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Things to Remember

• Enzymes are biological catalysts that drive chemical reactions and are required only in a small amount. They are capable of catalysing the conversion of substrate into product
• Enzymes are specific catalysts and are classified into 6 classes namely Oxidoreductases, Transferases, Hydrolases, Isomerases, Lyases, Ligases. 
• Enzymes increase the reaction rate
• Enzymes form complexes with their substrates
• Enzymes are affected by Ph and temperature
• Enzymes are sensitive to inhibitors
• Enzymes can be intracellular or extracellular 

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