Enzyme kinetics

Summary

This video explains enzyme kinetics, the study of how enzymes convert substrates into products. It covers essential terms such as Kcat (turnover number), which measures how many substrate molecules are converted per enzyme active site per second. The video discusses plotting substrate and product concentrations versus time, showing how reaction velocity increases with substrate concentration until reaching maximum velocity (Vmax). It also introduces Km, the substrate concentration at half Vmax, and explains how the ratio of Kcat to Km (specificity constant) reflects enzyme efficiency. The higher the ratio, the more efficient the enzyme.

Takeaways

• 😀 Enzyme kinetics studies how enzymes bind substrates and convert them into products during enzymatic reactions.
• 😀 The enzyme binds the substrate to form an enzyme-substrate (ES) complex, which typically exists in a transition state.
• 😀 The product is eventually released after being formed in the enzyme-substrate complex.
• 😀 The turnover number (k_cat) refers to the number of substrate molecules converted into product per active site per second.
• 😀 The unit of k_cat is seconds^(-1).
• 😀 Plotting concentration of substrates or products versus time helps understand enzyme kinetics.
• 😀 As substrate concentration decreases over time, the concentration of the product increases.
• 😀 The rate of reaction is the slope of the graph, representing the change in concentration of substrate or product per unit time.
• 😀 The rate of reaction for substrates is negative (due to consumption), while for products, it’s positive (due to formation).
• 😀 The velocity of a reaction increases with substrate concentration until it reaches a maximum velocity (V_max).
• 😀 The substrate concentration at which half of V_max is achieved is called the Michaelis constant (Km).
• 😀 Km is crucial for understanding enzyme efficiency and is defined as the substrate concentration at half of V_max.
• 😀 The ratio of k_cat to Km (specificity constant) measures enzyme efficiency; a higher ratio indicates greater efficiency.

Q & A

What is enzyme kinetics?

Enzyme kinetics is the study of how enzymes interact with substrates and convert them into products during enzymatic reactions.

What happens when an enzyme binds to a substrate?

When an enzyme binds to a substrate, it forms an enzyme-substrate (ES) complex, which often reaches a transition state where the substrate is converted into a product.

What is the turnover number (k-cat)?

The turnover number (k-cat) refers to the number of substrate molecules converted into a product per active site of the enzyme per second.

What are the units of k-cat?

The units of k-cat are seconds inverse (s^-1).

How can enzyme kinetics be analyzed graphically?

Enzyme kinetics can be analyzed by plotting the concentration of substrates or products against time. This helps to visualize the change in substrate concentration and product formation over time.

What does the slope of a concentration vs. time graph represent?

The slope of a concentration vs. time graph represents the rate of reaction, which is the change in concentration of substrate or product per unit time.

What is the rate of reaction in enzyme kinetics?

The rate of reaction refers to the change in concentration of substrate or product per unit time. For substrates, the rate is negative as concentration decreases, while for products, the rate is positive as concentration increases.

What happens to the velocity of the reaction when substrate concentration increases?

As substrate concentration increases, the velocity of the reaction also increases until it reaches a maximum value, known as V-max.

What is V-max?

V-max is the maximum velocity at which an enzyme catalyzes a reaction when the substrate concentration is saturating, meaning all enzyme active sites are occupied.

What is the significance of the Km value in enzyme kinetics?

Km, or the Michaelis constant, is the substrate concentration at which the reaction rate reaches half of V-max. It provides insight into the affinity of the enzyme for its substrate.

How is enzyme efficiency determined in enzyme kinetics?

Enzyme efficiency is determined by the ratio of k-cat to Km, known as the specificity constant. A higher ratio indicates a more efficient enzyme.