Cell biology and proposed mechanisms
Catalase
Catalase is an enzyme that breaks hydrogen peroxide down into water and oxygen. It is found in almost all aerobic organisms, concentrated in cell compartments called peroxisomes, and it is one of the fastest enzymes known — a single molecule can process millions of peroxide molecules per second.
Also called CAT, hydrogen peroxide oxidoreductase
What it does
Hydrogen peroxide is produced by superoxide dismutase and by several ordinary metabolic reactions. Left alone it can react with iron to form the far more damaging hydroxyl radical. Catalase converts it directly to water and oxygen, with no cofactor consumed. Glutathione peroxidase does a similar job at lower peroxide concentrations.
Catalase is one of the fastest enzymes known: a single molecule can process millions of peroxide molecules a second. It is concentrated in cell compartments called peroxisomes, and it is present in almost every organism that lives with oxygen.
Where it appears in ozone material
Catalase is commonly listed among the enzymes proposed to rise downstream of Nrf2, though the best-characterised Nrf2 target genes are others — NQO1, HO-1, GCLC/GCLM and glutathione reductase. That listing is why catalase appears in every account of the oxidative preconditioning hypothesis.
Bocci names catalase, together with glutathione peroxidase and free reduced glutathione, as the reason a transient rise in hydrogen peroxide inside blood cells is tolerated rather than toxic. Catalase activity was one of the biochemical parameters measured in the 1998 rat study in Mediators of Inflammation that first proposed ozone oxidative preconditioning.
Catalase also varies between organisms, which is one reason bacteria differ in how well they withstand oxidants — catalase testing is a routine technique in bacteriology.
Why it matters here
Catalase is the enzyme that clears hydrogen peroxide, and it is extraordinarily fast at it. It is the reason a brief rise in peroxide inside a cell is something the body is well equipped to deal with.