Antioxidative Enzymes in Humans

Enzymes are protein-based compounds that help biochemical reactions occur in your body. They may speed up reactions or help bring chemicals together, so they can best be described as catalysts. Oxidative enzymes catalyze oxidation reactions, which mean they grab a negatively charged electron or hydrogen atom from certain compounds and supply oxygen. Oxidative enzymes are present in virtually all the tissues of your body because they need oxygen to produce the energy needed to function. They also function as antioxidants because they are able to eliminate potentially harmful free radicals that are sometimes produced by oxidation reactions. The two most common types of oxidative enzymes are peroxidases and oxidases.

Peroxidases

Peroxidases are a large group of enzymes that use hydrogen peroxide to do their job. An important subgroup of peroxidases is based around the mineral selenium and called glutathione peroxidase, which includes eight similar molecules that function in humans. Their main biological role in the body is to protect your tissues from oxidative damage. Free radicals can trigger chain reactions in cells that lead to damage or death, but peroxidases are able to destroy them. Higher concentrations of oxygen are deadly to virtually all pathogenic microorganisms, so the glutathione family is also an important part of your immune system.

Oxidases

Oxidases are enzymes that use molecular oxygen, instead of hydrogen peroxide, to do their job. Both peroxidases and oxidases increase the rate at which ATP, the energy-storage molecule of your body, is produced aerobically. Oxidation reactions are a bit of a catch-22 in that they are essential for life, but they can also be damaging due to free radical production, so oxidative enzymes are complex compounds that serve a variety of regulatory roles. Oxidative enzymes also enlist the help of vitamins that are good antioxidants, such as vitamins A, C and E.

Other Notable Oxidative Enzymes

Other notable oxidative enzymes in your body are superoxide dismutase, catalase and succinic dehydrogenase. Superoxide dismutase enzymes are present in almost all aerobic cells and in extracellular fluids. They contain copper, zinc, manganese or iron as the backbone for their structures, so they are dependent on dietary minerals for effective function. Catalases use hydrogen peroxide to oxidate chemical reactions and kill free radicals, and are especially active in your blood. Succinic dehydrogenase is especially active in muscles and in the brain; low levels of this enzyme have been linked to degenerative brain diseases.

Changes in Enzyme Levels

The production and effectiveness of most oxidative enzymes often decrease with age, which helps explain why aging entails tissue damage and degeneration. Certain lifestyle choices, such as cigarette smoking and excessive alcohol intake, can deplete these enzymes and other antioxidants. Dietary deficiency in minerals, vitamins and protein also affect the production of enzymes. Exposure to high elevations, where the air contains less oxygen, increases oxidative enzyme activity, as does intense exercising. The importance of these enzymes and other antioxidants cannot be overstated because oxidation damage is linked to many serious diseases such as cancer, atherosclerosis, heart disease and neurological disorders.

 

References

  • Human Biochemistry; Charles Dreiling
  • General and Systematic Pathology; Paul Bass, et al.
  • Human Physiology: An Integrated Approach; Dee Silverthorn, et al.

About the Author

Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.