Characteristics of Enzymes

Characteristics of Enzymes

• Enzymes are macromolecules that act as biological catalysts, produced in living cells
• Most enzymes are globular proteins
• Enzymes lower the activation energy of a reaction, increasing the rate of reaction
• Enzymes are heat liable/sensitive
• Enzymes do not alter the nature or properties of the end products of a reaction
• Enzymes are highly specific to the substrate (substrate specific)
• Most enzyme-catalyzed reactions are reversible
• The rate of enzyme activity is affected by pH, temperature, and substrate concentrations
• Enzymes are not used up during a reaction
• Enzymes possess active sites where the reaction takes place
• Some enzymes need non-proteinous components (cofactors) to catalyze a reaction

Mechanisms of Enzyme Action

• The reactant that binds to an enzyme is called the substrate
• The enzyme binds to its substrate, forming an enzyme-substrate complex
• The catalytic action of the enzyme converts the substrate to the product
• The specificity of an enzyme results from its shape, which allows it to bind to a specific substrate
• The active site of an enzyme is formed by only a few amino acids
• The shape of the active site is complementary to the shape of the specific substrate
• Induced fit mechanism: the interactions between the substrate and active site may slightly change the shape of the active site, so that the substrate and active site become complementary to each other

Cofactors

• Cofactors are non-proteinous components essential for the catalytic activities of certain enzymes
• Cofactors bind to enzymes in two ways: tightly bound and loosely bound
• Examples of cofactors include derivatives of vitamins (co-enzymes) and inorganic ions (e.g. Zn2+, Fe2+, Cu2+)

Factors Affecting the Rate of Enzymatic Reactions

• Temperature: increases molecular motion, enhancing the speed of enzyme and substrate molecules, but can lead to denaturation of enzyme molecules beyond the optimum temperature
• pH: enzymes function most efficiently within a certain pH range, with alteration of pH leading to decline in enzyme activity
• Substrate concentration: increasing substrate concentration increases the probability of collision between the enzyme and substrate molecules, but enzyme molecules can become saturated
• Enzyme concentration: increasing enzyme concentration can increase the rate of reaction
• Inhibitors: substances that selectively bind to the enzyme, preventing the formation of an enzyme-substrate complex

Types of Inhibitors

• Competitive inhibitors: resemble the shape and nature of the substrate, competing with the substrate for the active site of the enzyme
• Non-competitive inhibitors: bind to a part of the enzyme other than the active site, causing a change in shape and making the active site less effective

Regulation Mechanism of Enzymatic Activity in Cells

• Allosteric regulation of enzymes: regulatory molecules bind to specific regulatory sites, affecting the shape and function of the enzyme
• Allosteric activation and inhibition: regulatory molecules bind to allosteric sites, stabilizing the active or inactive form of the enzyme
• Cooperativity: binding of one substrate molecule can stimulate binding or activity at other active sites, increasing catalytic activity
• Feedback inhibition: the end product of a metabolic pathway binds to an enzyme, inhibiting the production of more end products and regulating the metabolic process

Characteristics of Enzymes

• Enzymes are macromolecules that act as biological catalysts, produced in living cells
• Most enzymes are globular proteins
• Enzymes lower the activation energy of a reaction, increasing the rate of reaction
• Enzymes are heat liable/sensitive
• Enzymes do not alter the nature or properties of the end products of a reaction
• Enzymes are highly specific to the substrate (substrate specific)
• Most enzyme-catalyzed reactions are reversible
• The rate of enzyme activity is affected by pH, temperature, and substrate concentrations
• Enzymes are not used up during a reaction
• Enzymes possess active sites where the reaction takes place
• Some enzymes need non-proteinous components (cofactors) to catalyze a reaction

Mechanisms of Enzyme Action

• The reactant that binds to an enzyme is called the substrate
• The enzyme binds to its substrate, forming an enzyme-substrate complex
• The catalytic action of the enzyme converts the substrate to the product
• The specificity of an enzyme results from its shape, which allows it to bind to a specific substrate
• The active site of an enzyme is formed by only a few amino acids
• The shape of the active site is complementary to the shape of the specific substrate
• Induced fit mechanism: the interactions between the substrate and active site may slightly change the shape of the active site, so that the substrate and active site become complementary to each other

Cofactors

• Cofactors are non-proteinous components essential for the catalytic activities of certain enzymes
• Cofactors bind to enzymes in two ways: tightly bound and loosely bound
• Examples of cofactors include derivatives of vitamins (co-enzymes) and inorganic ions (e.g. Zn2+, Fe2+, Cu2+)

Factors Affecting the Rate of Enzymatic Reactions

• Temperature: increases molecular motion, enhancing the speed of enzyme and substrate molecules, but can lead to denaturation of enzyme molecules beyond the optimum temperature
• pH: enzymes function most efficiently within a certain pH range, with alteration of pH leading to decline in enzyme activity
• Substrate concentration: increasing substrate concentration increases the probability of collision between the enzyme and substrate molecules, but enzyme molecules can become saturated
• Enzyme concentration: increasing enzyme concentration can increase the rate of reaction
• Inhibitors: substances that selectively bind to the enzyme, preventing the formation of an enzyme-substrate complex

Types of Inhibitors

• Competitive inhibitors: resemble the shape and nature of the substrate, competing with the substrate for the active site of the enzyme
• Non-competitive inhibitors: bind to a part of the enzyme other than the active site, causing a change in shape and making the active site less effective

Regulation Mechanism of Enzymatic Activity in Cells

• Allosteric regulation of enzymes: regulatory molecules bind to specific regulatory sites, affecting the shape and function of the enzyme
• Allosteric activation and inhibition: regulatory molecules bind to allosteric sites, stabilizing the active or inactive form of the enzyme
• Cooperativity: binding of one substrate molecule can stimulate binding or activity at other active sites, increasing catalytic activity
• Feedback inhibition: the end product of a metabolic pathway binds to an enzyme, inhibiting the production of more end products and regulating the metabolic process