Catalase enzymes, or catalases, trigger the rapid conversion of hydrogen peroxide into biologically safe substances, like water. Hydrogen peroxide is a potentially dangerous side effect of the metabolism of oxygen, a process that occurs in most living things, from aerobic bacteria to plants and animals. Like other enzymes, catalases are specialized large protein molecules. They may have a function in preventing the formation of reactive molecules called radicals that play a role in causing DNA mutations associated with cancer. Some scientific evidence suggests diminished enzyme activity in aging may underlie the whitening of hair in humans.
The primary function of catalase enzymes is the rapid breakdown of hydrogen peroxide into water and safe oxygen compounds. Many metabolic pathways in organisms produce hydrogen peroxide as a by-product of other chemical reactions. If it were left in living tissues, this could cause extensive cellular damage that would quickly endanger the organism if the accumulation continued unchecked. For this reason, these enzymes are necessary parts of normal cellular equipment. They are found in the vast majority of living cells and nearly every aerobic cell.
Though it presents dangers like the production of hydrogen peroxide, oxygen metabolism is one of the most common metabolic processes among life on Earth. Oxygen can be converted into molecules called superoxide radicals, which strip away important metal atoms from many biological proteins, changing their function. Without catalases to metabolize it, hydrogen peroxide also can be transformed into reactive molecules that can cause damage to DNA, increasing the risk of cancer because of possible mutations. Scientific studies have not fully established the relationship between diminished catalase enzyme activity and tumor formation, however, a connection further complicated by the fact that several other enzymes also metabolize radicals and peroxide.
All enzymes are protein macromolecules composed of many specific amino acid molecules. In addition to converting hydrogen peroxide to water, catalases can oxidize various toxic organic chemicals like phenols. These enzymes share a space within cells in a compartment called a peroxisome, which contains enzymes important for lipid metabolism and for the decomposition of dangerous oxygen compounds like hydrogen peroxide.
With age, the amount of catalase enzymes produced in the human body appears to diminish. Some scientific studies of hydrogen peroxide metabolism indicate it interferes with the biological pigment melanin, which is responsible for hair and skin coloration. Researchers suggested that the whitening or graying of hair occurs due to a gradual accumulation of hydrogen peroxide in tissues without sufficient amounts of it being cleared out of the system as water. Individuals with acatalasia, a rare hereditary disease, produce none of this enzyme yet have no significantly higher illness risk, which has led scientists to speculate that mammals may rely on other enzymes for much of their peroxide metabolism.