Catalase is an enzyme found in nearly all living organisms exposed to oxygen. An “assay” refers to a laboratory method used to measure the amount or activity of a substance. A catalase activity assay is a procedure designed to quantify how effectively this enzyme performs its biological function.
What Catalase Does
Catalase breaks down hydrogen peroxide (H₂O₂), a byproduct of many normal metabolic processes. Hydrogen peroxide is a reactive oxygen species (ROS) and can be harmful if allowed to accumulate within cells and tissues. Catalase rapidly converts hydrogen peroxide into less reactive substances: water (H₂O) and gaseous oxygen (O₂).
One catalase molecule can convert millions of hydrogen peroxide molecules to water and oxygen each second. In eukaryotic cells, catalase is located within peroxisomes, organelles that produce hydrogen peroxide. Catalase then neutralizes this toxic byproduct.
Why Catalase Activity Matters
Measuring catalase activity is important because changes in its levels or function can indicate various physiological states and health conditions. An imbalance between free radical production and the body’s ability to neutralize them leads to oxidative stress, which catalase helps to mitigate.
Low levels or impaired function of catalase are associated with increased oxidative stress and cellular damage. This imbalance has been linked to various age-associated degenerative diseases such as diabetes mellitus, hypertension, anemia, Alzheimer’s disease, Parkinson’s disease, and certain cancers. For instance, reduced catalase activity can lead to hydrogen peroxide accumulation, which may contribute to the graying of human hair by interfering with melanin production. In conditions like asthma, decreased antioxidant enzyme activity, including catalase, contributes to chronic airway inflammation.
Measuring Catalase Activity
Measuring catalase activity involves quantifying the rate at which it breaks down hydrogen peroxide. Scientists can assess this by observing either the disappearance of the hydrogen peroxide substrate or the production of oxygen gas.
One approach measures the reduction in hydrogen peroxide absorbance at a specific wavelength, typically around 240 nm, using a spectrophotometer. As catalase breaks down hydrogen peroxide, the absorbance at this wavelength decreases, and the rate of this decrease is proportional to the enzyme’s activity. Another method involves adding hydrogen peroxide to a sample containing catalase and visually observing the rapid production of oxygen bubbles, with the height of the foam indicating the level of activity.
Many modern assays quantify catalase activity by incubating a sample containing the enzyme with a known concentration of hydrogen peroxide. After a set incubation period, the reaction is stopped, and the remaining hydrogen peroxide is quantified, often through a colorimetric reaction that changes absorbance in the visible light spectrum, typically around 520 nm. This approach helps to minimize interference from other biological components that might absorb light in the ultraviolet range.
Where Catalase Assays Are Used
Catalase activity assays find broad application across various fields. In medical research, these assays investigate the role of oxidative stress in disease progression and evaluate potential therapeutic interventions. For example, altered catalase activity can be a marker for inflammation or cellular injury in conditions like inflammatory bowel disease or neurodegenerative disorders.
In the food industry, catalase assays are employed for quality control and to extend product shelf life. Catalase can be used to remove residual hydrogen peroxide from milk before cheese production or to prevent food oxidation in packaging. The enzyme also finds use in the textile industry to remove hydrogen peroxide from fabrics after bleaching, ensuring the material is peroxide-free. Catalase assays are also applied in environmental monitoring, as indicators of stress in organisms exposed to pollutants, and in biotechnology for bioremediation processes.