We can't live without oxygen. Our cells rely on oxygen as the final acceptor of electrons in respiration, allowing us to extract far more energy from food than would be possible without oxygen. But oxygen is also a dangerous compound. When it reacts with other molecules, it can produce reactive oxygen species (ROS) that can damage cells. To prevent this damage, our cells have evolved multiple mechanisms to keep ROS levels in check.
One important way that cells control ROS levels is through the use of enzymes called antioxidant enzymes. Antioxidants are substances that can prevent or slow damage to cells caused by free radicals, unstable molecules that the body produces as a response to environmental and other pressures. The body also needs antioxidant enzymes to clean up these dangerous molecules.
There are many types of antioxidant enzymes, each with a specific role to play in protecting cells from ROS. One important type of antioxidant enzyme is superoxide dismutase (SOD). Dismutase in this context means to break down, and SOD breaks down SO into oxygen and hydrogen peroxide. While hydrogen peroxide is itself a reactive compound, but it is not as reactive as superoxide, it can still damage cells. To prevent this, another type of antioxidant enzyme, catalase, breaks down hydrogen peroxide into water and oxygen. SOD and catalase are just two of the many antioxidant enzymes that our cells use to control ROS levels. These enzymes are essential for keeping our cells healthy and preventing disease.
Cu/Zn superoxide dismutase is a very efficient enzyme.
Zn is an important mineral for the body because it helps to protect cells from damage. Researchers have determined that one out of every ten collisions between superoxide (SO) and the enzyme will lead to a reaction. This is far more than expected, since the active site covers only a small portion of the enzyme surface, and we might expect that most collisions would occur somewhere else on the surface.
The shape and characteristics of the active site, however, may give some hints to this efficiency. The active site is funnel-shaped, with copper and zinc (colored green here) at the base of the funnel. The strong positive charge of the metal ions, along with two nearby positively-charged amino acids (colored blue here), serve to draw the negatively-charged SO (red) into the funnel.
Structure of Structure Cu/Zn superoxide dismutase
Superoxide Dismutases: Role in Redox Signaling, Vascular Function, and Diseases.
SOD has recently gained notoriety for its connection with amyotrophic lateral sclerosis, more commonly known as Lou Gehrig's disease. Recent research has shown that one of the mutations is found in the gene for SOD. Scientists are now studying the role of SOD in the disease, hoping that this knowledge will lead to new treatments and cures.
The list of pathophysiological conditions that are associated with the overproduction of SO anions expands every day. The most exciting realization is that there seems to be a similarity between the tissue injury that is observed in various disease states, as SO anions produce tissue injury and associated inflammation in all tissues in similar ways.
Tissue injury and inflammation form the basis of many disease pathologies, including ischemia and reperfusion injuries, radiation injury, hyperoxic lung damage, and atherosclerosis. This commonality provides a unique opportunity to manipulate numerous disease states with an agent that removes SO anions.
Superoxide anions produce tissue injury and associated inflammation