Living cells are naturally designed to be able to protect themselves. Some threats to cells come from chemicals that are generated in the cells themselves. To combat these harmful chemicals, cells create enzymes which can convert dangerous chemicals into harmless ones. One such enzyme, known as catalase, works to detoxify hydrogen peroxide.
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Hydrogen peroxide is a chemical that can be accidentally produced in cells, the Protein Data Bank explains. Many cells, including human cells, utilize oxygen in a variety of chemical reactions. Sometimes this oxygen reacts with other nearby compounds and forms the chemical hydrogen peroxide. Hydrogen peroxide can react with certain molecules inside of cells and cause damage to proteins and important cellular structures. In addition, hydrogen peroxide can be turned into hydroxyl radicals, which is a type of free radical. Free radicals are unstable molecules that can set off damaging chain reactions within cells. Catalase is designed to eliminate hydrogen peroxide from cells.
Catalase is an enzyme, which means that it speeds up chemical reactions that would otherwise occur very slowly within cells. The reaction that catalase speeds up is the break down of two molecules of hydrogen peroxide, into two molecules of water and one molecule of oxygen gas. Because catalase produces oxygen, it is generally only found in organisms which can survive in the presence of oxygen; these organisms are known as aerobes.
The catalase protein is a tetramer, which means that it is made up of four protein subunits, according to the Biomolecules at Kenyon College website. In addition to these four protein subunits, catalase also contains a heme and a nicotinamide adenine dinucleotide phosphate molecule, commonly referred to as NADP; these two molecules are also necessary for the enzyme to function properly. Although there are slight differences in the catalase structure among the types found in different organisms, the overall structure of four protein subunits combined with a heme and NADP molecule.
Catalase and Bacteria
Catalase is found in many oxygen-growing bacteria. This works as a protective mechanism for bacteria, as some immune cells generate hydrogen peroxide to kill infectious bacterial cells. Catalase can also be used in laboratories as part of a regimen of tests to identify bacteria based on their characteristics; the bacteria are treated with a small amount of hydrogen peroxide; if bubbles form, the bacteria have the catalase enzyme.
Catalase and Gray Hairs
Catalase may also be tied to the graying of hair. A 2009 article in Science Daily cites research that found that gray hairs are caused by the accumulation of hydrogen peroxide in hair follicles. The hydrogen peroxide is able to bleach hair only if the levels of catalase in the hair follicle cells decrease.