Peroxidase
Peroxidase is an enzyme that acts as a catalyst in biological processes involving oxidation, facilitating the conversion of harmful peroxides into less toxic substances. These enzymes play a crucial role in both plants and animals, promoting the oxidation of compounds without damaging cells. They are particularly important in detoxifying systems, where they help manage reactive oxygen species that can cause cellular damage, especially during stress conditions in plants such as pest attacks or drought. The discovery of hydrogen peroxide by French chemist Louis Jacques Thénard in 1818 laid the groundwork for understanding peroxidases, as he noted their ability to convert hydrogen peroxide into water and oxygen.
In mammals, peroxidases are involved in various biochemical reactions, including the production of essential thyroid hormones. Salivary peroxidases contribute to oral health by catalyzing reactions that have antimicrobial properties. In plants, peroxidases not only mitigate oxidative stress but also have significant applications in fields such as microbiology and histochemistry. For example, horseradish peroxidase is extensively used in diagnostic procedures and environmental applications, including the treatment of textile dyes and industrial waste. Overall, peroxidases are vital components in maintaining biological balance and facilitating various chemical reactions essential for life.
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Peroxidase
A peroxidase is a type of enzyme that behaves as a catalyst, or a material that enables a chemical reaction without being a part of it, in a range of biological processes that involve oxidation. When a compound is oxidized, it gains oxygen. In plants and animals, peroxidase fosters the oxidation of compounds by peroxides—toxic, highly reactive oxidizing agents often formed during biochemical reactions—in a way that does not damage cells. Specifically, when catalyzing the oxidation of a compound, peroxidases use peroxides in a reduction-oxidation reaction that binds hydrogen to the compound and forms water as a byproduct.
Overview
In 1818, French chemist Louis Jaques Thénard (1777–1857) discovered hydrogen peroxide and was the first to produce the molecule in the laboratory. He also observed that several animals and plants are able to convert hydrogen peroxide into water and oxygen. Thénard’s work with hydrogen peroxide reactions led to the discovery of catalysts in general and peroxidases in particular.
Peroxidases are found in both animals and plants. In mammals, including humans, various peroxidases act as detoxifying agents. Selenium-containing peroxidase enzymes known as glutathiones catalyze reactions that use hydrogen peroxide; other glutathiones are catalysts for reactions involving peroxide-lipid compounds.
Thyroid peroxidase, also known as thyroperoxidase (TPO), exists mainly in the thyroid gland and aids the release of iodine from nutrients to create essential thyroid hormones. A TPO antibody test can help physicians determine if a patient’s thyroid disease is caused by an autoimmune disorder such as Graves disease or Hashimoto’s disease. Saliva also contains peroxidases, which catalyze reduction-oxidation reactions between hydrogen peroxide and thiocyanate. Such reactions form compounds that have antimicrobial effects.
Plants contain a variety of peroxidases. These peroxidases remove what are known as reactive oxygen species, such as hydrogen peroxide and other oxygen forms or compounds that are unstable and can harm or destroy cells. Plants tend to release reactive oxygen species when stressed by pests, drought, heat, or other adverse conditions. By limiting the damage caused by reactive oxygen species, peroxidases help plants survive such stresses.
Plant peroxidases have several important applications in microbiology as well as histochemistry, which is the science of identifying the composition and distribution of the chemicals that make up tissues of living organisms. Horseradish peroxidase (HRP) is used in these fields in a variety of diagnostic procedures, including the TPO antibody test, urine and serum glucose tests, and cancer biopsy stains. HRP and other plant peroxidases have also been used to bleach and remove toxic compounds from textile dyes and industrial effluents.
Bibliography
Bogaert, Lucas, and Noah Coppens, eds. Peroxidases: Biochemical Characteristics, Functions and Potential Applications. Hauppage: Nova Sci., 2013. Digital file.
Gómez, J. L., M. Gómez, and M. D. Murcia. “Soybean, a Peroxidase Source for the Biotreatment of Effluents.” Soybeans: Cultivation, Uses, and Nutrition. Ed. Jason E. Maxwell. Hauppage: Nova Sci., 2011. 155–87. Digital file.
Hofrichter, M., et al. “New and Classic Families of Secreted Fungal Heme Peroxidases.” Applied Microbiology and Biotechnology 87.3 (2010): 871–97. Print.
Petrides, Petro E., and William M. Nauseef. The Peroxidase Multigene Family of Enzymes: Biochemical Basis and Clinical Applications. Berlin; New York: Springer, 2000. Print.
Ream, Amanda. “The Secret Life of Horseradish.” Mother Earth News June–July 1995: 14+. Print.
Saunders, Bernard Charles, Andrew Gordon Holmes-Siedle, and Bernard Peter Stark. Peroxidase: The Properties and Uses of a Versatile Enzyme and of Some Related Catalysts. Washington: Butterworth, 1964. Print.
Szajdak, Lech W., and Teresa Meysner. “Iron Forms and Peroxidase Activity in Forest Island Soils.” Estonian Journal of Ecology 62.2 (2013): 81–99. Print.
Torres, Eduardo, and Marcela Ayala, eds. Biocatalysis Based on Heme Peroxidases: Peroxidases as Potential Industrial Biocatalysts. Berlin: Springer, 2010. Print.
Veitch, Nigel C. “Horseradish Peroxidase: A Modern View of a Classic Enzyme.” Phytochemistry 65.3 (2004): 249–59. Print.