Several antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase etc. The best studied cellular antioxidants are the enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase. Mammalian cells are protected by presence of catalase, glutathione, peroxidases, and superoxide dismutase. It produces oxidase, catalase, and urease. Hydrogen peroxide can also be decomposed biologically by the enzyme catalase. I activity in mitochondria, and increase activity of the antioxidant enzyme catalase. It tests negative for cytochrome, oxidase, and catalase, and positive for alpha-hemolytic activity. They are facultatively anaerobic and give negative reactions to both oxidase and catalase tests. It is positive for catalase and oxidase reactions. It is citrate, catalase, and oxidase positive. They are positive by the oxidase test and catalase test. Another example is the chemical decomposition of hydrogen peroxide carried out by the enzyme catalase. Hydrogen peroxide is also damaging and is degraded by other enzymes such as catalase. Hydrogen peroxide can then be broken down by another enzyme called catalase. All the medically significant species of "Neisseria" are positive for both catalase and oxidase.