Turnover Number

Definition

Turnover number, often denoted as k_cat, is a measure of the efficiency of an enzyme, defined as the number of substrate molecules converted to product by an enzyme molecule per unit time when the enzyme is fully saturated with substrate. This metric highlights how effectively an enzyme operates under optimal conditions and can provide insight into its catalytic efficiency compared to other enzymes. It is a crucial concept in understanding enzyme kinetics and plays a significant role in biochemical processes.

5 Must Know Facts For Your Next Test

1. Turnover number is expressed in units of time, typically seconds, reflecting how many substrate molecules are transformed by one enzyme molecule per second at saturation.
2. A higher turnover number indicates a more efficient enzyme, which can be critical for understanding metabolic pathways and drug interactions.
3. Turnover numbers can vary widely between different enzymes; for example, carbonic anhydrase has a turnover number of about 1 million per second.
4. The turnover number is directly influenced by factors such as temperature, pH, and the presence of inhibitors or activators.
5. In practical applications, knowing the turnover number can help in enzyme engineering and designing drugs that target specific enzymes more effectively.

Review Questions

• How does the turnover number relate to an enzyme's efficiency and its operational conditions?
  • Turnover number is a key indicator of an enzyme's efficiency, showing how many substrate molecules it can convert to product per unit time when saturated with substrate. A high turnover number signifies that the enzyme can perform its catalytic function rapidly under optimal conditions. Factors such as temperature and pH can influence this efficiency, demonstrating how important it is to consider environmental conditions when evaluating enzyme performance.
• Discuss the significance of the turnover number in the context of enzyme kinetics and its applications in biochemistry.
  • The turnover number is central to enzyme kinetics because it provides quantitative data on how effectively an enzyme catalyzes reactions. By comparing turnover numbers among different enzymes, researchers can assess their relative efficiencies, leading to insights into metabolic pathways. This information is crucial for applications like drug design, where understanding how drugs interact with enzymes can lead to better therapeutic strategies.
• Evaluate how knowledge of the turnover number can impact pharmaceutical development and enzyme engineering strategies.
  • Knowledge of the turnover number can significantly influence pharmaceutical development by guiding the design of drugs that effectively target specific enzymes. Understanding an enzyme's efficiency allows researchers to optimize drug concentrations and improve therapeutic outcomes. Additionally, in enzyme engineering, turnover numbers can inform modifications to enhance or inhibit enzymatic activity, tailoring enzymes for industrial processes or therapeutic use, ultimately leading to more effective treatments and biocatalysts.

Related terms

Enzyme Kinetics: The study of the rates at which enzyme-catalyzed reactions occur and the factors that influence these rates.

Michaelis-Menten Equation: A mathematical model that describes the rate of enzyme-catalyzed reactions, establishing a relationship between substrate concentration and reaction velocity.

Catalytic Efficiency: A measure that combines both the turnover number and the affinity of an enzyme for its substrate, usually expressed as k_cat/K_m.