Principles of Enzymology and Its Biotechnological Applications

Enzymes are highly efficient and specific biological catalysts, most of which are proteins. They can significantly accelerate the rate of biochemical reactions without altering the reaction equilibrium. Their catalytic mechanism depends on a unique spatial conformation and active site, promoting substrate conversion to product by lowering the activation energy of the reaction.

I. Basic Characteristics of Enzymes

Enzymes are proteins or RNA molecules with catalytic activity. Their main features include:

• High efficiency: Catalytic efficiency can be millions of times higher than that of chemical catalysts.

• Specificity: Exhibited as substrate specificity and reaction specificity.

• Function under mild conditions: Active under physiological temperature, normal pressure, and neutral pH.

• Regulability: Activity can be modulated by environmental factors, allosteric effects, and covalent modifications.

II. Principles of Enzyme Catalysis

Enzymes accelerate reactions by lowering the activation energy (Ea) required, without changing the reaction equilibrium. The mechanisms include:

• Lock-and-key and induced fit models: Explain how enzymes bind to substrates.

• Transition state stabilization: Formation of a transition-state complex reduces activation energy.

• Microenvironment effects: The active site provides an optimal chemical environment to facilitate the reaction.

III. Enzyme Kinetics

Enzyme kinetics studies the effects of enzyme concentration, substrate concentration, temperature, pH, and other factors on reaction rate. Core theories and methods include:

1.Initial rate (v₀): The “reference indicator” for kinetic analysis

At the early stage of an enzyme-catalyzed reaction, substrate concentration is highest and product concentration is negligible (reverse reaction can be ignored). The rate measured at this point is called the initial rate (v₀), which is approximately constant over a short time, avoiding interference from product inhibition or substrate depletion. It forms the basis for calculating kinetic parameters.

2.Michaelis-Menten equation: Relationship between substrate concentration and reaction rate

• Vmax (maximum reaction rate): The rate when all enzyme active sites are saturated with substrate, proportional to total enzyme concentration, reflecting the enzyme’s maximum catalytic capacity.

• Km (Michaelis constant): Substrate concentration at which the reaction rate reaches Vmax/2. It characterizes enzyme affinity for the substrate—smaller Km indicates stronger affinity and efficient catalysis at low substrate concentrations. Km usually approximates physiological substrate concentrations, allowing sensitive enzymatic response to substrate changes.

3.Lineweaver-Burk plot: Accurate determination of kinetic parameters

• Y-intercept = 1/Vmax

• X-intercept = -1/Km

• Slope = Km/Vmax

IV. Factors Affecting Enzyme Activity

1.pH: The “acid-base environment” affecting activity

Each enzyme has an optimal pH (pHopt). Deviation from this optimum can alter the ionization state of key residues in the active site, and extreme pH may cause irreversible inactivation.

2.Temperature: A “double-edged sword”

Increasing temperature initially enhances molecular motion, raising reaction rates. Excessive heat causes protein denaturation and rapid loss of activity. The optimal temperature (Tₒₚₜ) corresponds to the peak activity.

V. Enzyme Inhibition and Regulation

1.Reversible inhibition (non-covalent, reversible)

Inhibition type	Mechanism	Effect on kinetic parameters	Typical example
Competitive inhibition	Inhibitor resembles substrate, competing for the active site	Km increases, Vmax unchanged	Statins inhibiting HMG-CoA reductase (cholesterol-lowering)
Non-competitive inhibition	Inhibitor binds to non-active site (allosteric site), altering enzyme conformation	Vmax decreases, Km unchanged	Heavy metal ions inhibiting certain oxidases
Uncompetitive inhibition	Inhibitor binds only to enzyme-substrate complex (ES) to form inactive ESI	Km and Vmax both decrease	Cyanide inhibiting alkaline phosphatase

2.Irreversible inhibition (covalent, permanent inactivation)

Inhibitors form stable covalent bonds with key groups in the active site (e.g., thiol, hydroxyl), causing permanent enzyme inactivation. Typical examples include heavy metals (mercury, lead), organophosphate pesticides (cholinesterase inhibitors), and chemical toxins (e.g., sarin).

3.Allosteric regulation: “Switch control” of metabolic pathways

• Core features: Allosteric enzymes are often key metabolic enzymes; their rate-substrate concentration curves are sigmoidal (S-shaped), showing cooperative effects and sharp changes in activity within narrow substrate concentration ranges, allowing precise metabolic flux control.

• Mechanism: Multi-subunit enzymes contain active sites and regulatory sites. Regulatory molecules (usually intermediates or end products of metabolism) bind to regulatory sites, altering conformation and substrate affinity.

• Typical example: Feedback inhibition, such as ATP inhibiting phosphofructokinase, a key enzyme in glycolysis, preventing excessive product accumulation and energy waste.

Related Products

Name	ID	Grade & Purity
Horseradish Peroxidase (HRP)	P105528	EnzymoPure™, ≥250 U/mg，Rz≥3
β-Galactosidase from Escherichia coli	G128642	EnzymoPure™, ≥50 units/mg dry weight
L-Lactate Dehydrogenase (L-LDH)	L196994	EnzymoPure™, ActiBioPure™, Bioactive, High Performance, ≥90%(SDS-PAGE), ≥300 U/mg protein
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Glucose-oxidase	G757809	EnzymoPure™, 13000 GODU/g
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