Catalase
Catalase is an essential enzyme found in various living organisms that is responsible for catalyzing the breakdown of hydrogen peroxide, a reactive by-product of oxygen metabolism, into harmless water and oxygen. As a powerful antioxidant enzyme, catalase helps protect cells from oxidative damage caused by reactive oxygen species (ROS), which can lead to harmful effects on cellular structures, including DNA. It works in conjunction with another enzyme, superoxide dismutase, to efficiently manage oxidative stress by converting ROS into hydrogen peroxide, which is then further decomposed by catalase.
The enzyme is composed of polypeptide chains, rich in iron ions, which facilitate its interaction with hydrogen peroxide. Catalase is predominantly found in the liver of mammals, although its structure can vary between species, with different forms present in plants and bacteria. Additionally, catalase plays a vital role in various industrial applications, including food preservation and wastewater treatment. Low levels of this enzyme have been associated with the graying of hair, indicating its significance in cellular health. Understanding catalase is crucial for exploring its protective functions and potential implications for health and disease management.
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Catalase
Catalase is a bodily enzyme found in living organisms exposed to oxygen. Enzymes are biological catalysts, meaning they speed up the process of a chemical reaction in an organism. Catalase speeds up the chemical reaction that leads to the decomposition of hydrogen peroxide. The result of this decomposition reaction is that hydrogen peroxide breaks down into water and oxygen. Catalase is one of the most active enzymes in the body and is capable of converting millions of hydrogen peroxide molecules into water and oxygen every second. Catalase plays an important protective role in cells. It shields cells from destruction by oxidative damage caused by chemically reactive species known as reactive oxygen species (ROS). Since catalase protects the cells from damage caused by oxygen reactions, it is referred to as an antioxidant enzyme. Alongside its protective properties, catalase also mobilizes hydrogen peroxide to neutralize harmful toxins that enter the body such as methanol, ethanol, and formaldehyde. Outside its natural biological function, catalase is also used at an industrial level in the preservation and manufacture of foodstuffs and to break down hydrogen peroxide found in wastewater.
Background
Oxygen is an elemental gas that plays an important role in living things by providing fuel to the cells so they can carry out their biological duties. Oxygen is a highly reactive molecule, so an organism must keep the element in check to ensure it only carries out specific functions in cells. Oxygen can be easily converted into reactive compounds if left unchecked.
Organisms did not always utilize oxygen for fuel, but this evolutionary shift led to a number of biological advantages, such as the ability to produce more energy from food breakdown. These advantages came at a price, however, in the form of oxygen by-products known as reactive oxygen species (ROS), which include hydrogen peroxide, superoxide anion radicals, singlet oxygen, hydroxyl radicals, and nitric oxide. Although these substances carry out normal functions within organisms, if they are not carefully regulated, ROS can damage molecules in cells and lead to oxidative stress.
Inside an organism’s cells lies a structure called the nucleus, which is surrounded by components called electrons. The electrons surrounding the nucleus determine what type of chemical reactions can occur between molecules. Electrons are transferred from one site to another by carrier molecules. If oxygen comes into contact with one of these carrier molecules during transference, an electron may mistakenly transfer to the oxygen molecule. This can lead to reactions that convert oxygen into ROS. These compounds are very reactive and can cause damage to many important macromolecules in the body, such as important proteins. Some ROS can even damage DNA, and a popular though unproven scientific theory holds that DNA damage caused by ROS is the cause of aging.
Catalase plays a major role in managing dangerous oxygen reactions. The enzyme works in conjunction with another enzyme, superoxide dismutase, which converts the ROS superoxide anion radicals into hydrogen peroxide. Hydrogen peroxide is then converted into harmless water and oxygen by catalase. Catalase is present in large quantities throughout organisms and is found primarily in the liver in mammals. It is on constant guard against cell damage as it maintains safe levels of hydrogen peroxide.
Overview
The enzyme catalase is a type of protein with four subunits of polypeptide chains, or chains of amino acids that form the basis of protein molecules. Catalase’s polypeptide chains contain more than five hundred amino acids each. Catalase also contains iron ions, which allow it to react with hydrogen peroxide. Although catalase’s general composition is similar throughout organisms, different organisms produce different forms of catalase. Catalase found in animals is of a slightly different structure than the catalase found in plants.
Since catalase is consistently fighting against reactive molecules, it is one of the most highly stable enzymes, and its chains interweave to lock its full complex tightly together. Different cells produce different kinds of catalase. Catalase that protects red blood cells is made of four identical subunits and utilizes an iron group to execute a reaction. Bacteria, on the other hand, create a larger type of catalase with a structure that uses manganese instead of iron to perform a reaction.
Prior to the arrival of catalase, an enzyme called superoxide dismutase breaks down the ROS superoxide anion radicals into hydrogen peroxide and oxygen. Catalase then comes in to break down hydrogen peroxide through a two-stage mechanism. In the first stage, a hydrogen peroxide molecule binds to catalase and then breaks apart. One oxygen atom is removed and attaches to the iron atom in the catalase. The remaining hydrogen and oxygen is released as water. In the second stage, another hydrogen peroxide molecule binds to the catalase with the oxygen atom attached. This second hydrogen peroxide molecule is broken down and combined with the oxygen atom bound to the iron in the catalase. This leads to a release of water and oxygen gas.
Mutations in either superoxide dismutase or oxygen can lead to harmful health effects in organisms. In humans, malfunction of the superoxide dismutase enzyme can lead to extreme damage caused by superoxide anion radicals. Without superoxide dismutase to properly perform the breakdown of the superoxide anion radicals, catalase cannot perform its function properly. Such a mutation can lead to oxidative stress that causes amyotrophic lateral sclerosis (ALS), a disease of the nervous system that destroys neurons that control voluntary muscles. Catalase protects cells from oxidative stress that can lead to many types of biological disorders.
Bibliography
Boon, Elizabeth M, et al. “Catalase: H2O2: H2O2 Oxidoreductase.” Kenyon College, biology.kenyon.edu/BMB/Chime/catalase/frames/cattx.htm. Accessed 9 Jan. 2019.
“CAT Catalase [Homo sapiens (Human)].” National Center for Biotechnology Information, 10 Dec. 2024, www.ncbi.nlm.nih.gov/gene/847. Accessed 18 Dec. 2024.
“Catalase.” Protein Data Bank, pdb101.rcsb.org/motm/57. Accessed 18 Dec. 2024.
“Catalase.” Worthington Biochemical Corporation, www.worthington-biochem.com/ctl/default.html. Accessed 18 Dec. 2024.
"Giving Catalase the Recognition It Deserves." Biosynth, 8 July 2024, www.biosynth.com/blog/giving-catalase-the-recognition-it-deserves. Accessed 18 Dec. 2024.
McDowall, Jennifer. “How Catalase Works.” European Molecular Biology Laboratory, www.ebi.ac.uk/interpro/potm/2004‗9/Page2.htm. Accessed 18 Dec. 2024.