Enzyme Action: Testing Catalase Activity

Introduction

Many organisms can decompose hydrogen peroxide (H₂O₂) enzymatically. Enzymes are globular proteins, responsible for most of the chemical activities of living organisms. They act as catalysts, substances that speed up chemical reactions without being destroyed or altered during the process. Enzymes are extremely efficient and may be used over and over again. One enzyme may catalyze thousands of reactions every second. Both the temperature and the pH at which enzymes function are extremely important. Most organisms have a preferred temperature range in which they survive, and their enzymes most likely function best within that temperature range. If the environment of the enzyme is too acidic or too basic, the enzyme may irreversibly denature, or unravel, until it no longer has the shape necessary for proper functioning.

H₂O₂ is toxic to most living organisms. Many organisms are capable of enzymatically destroying the H₂O₂ before it can do much damage. H₂O₂ can be converted to oxygen and water, as follows:

Although this reaction occurs spontaneously, the enzyme catalase increases the rate considerably. Catalase is found in most living organisms. A great deal can be learned about enzymes by studying the rates of enzyme-catalyzed reactions.

Objectives

In this experiment, you will

• Use an Oxygen Gas Sensor to measure the production of oxygen gas as hydrogen peroxide is destroyed by the enzyme catalase or peroxidase at various enzyme concentrations.
• Measure and compare the initial rates of reaction for this enzyme when different concentrations of enzyme react with H₂O₂.
• Measure the production of oxygen gas as hydrogen peroxide is destroyed by the enzyme catalase or peroxidase at various temperatures.
• Measure and compare the initial rates of reaction for the enzyme at each temperature.
• Measure the production of oxygen gas as hydrogen peroxide is destroyed by the enzyme catalase or peroxidase at various pH values.
• Measure and compare the initial rates of reaction for the enzyme at each pH value.