ABSTRACT
A series of organelles isolated from mammalian organs and other aerobic eukary otic cells have been described as sources of superoxide radical anion (0 2~) and hydrogen peroxide (H20 2). These two molecules, the products of the univalent and bivalent reduction of oxygen, are physiologically produced as a characteristic of aerobic metabolism and constitute normal intracellular metabolites. Superox ide radical is produced from one-electron transfer to the oxygen molecule, which originates a chemical species with an odd number of electrons, in other words an oxygen free radical, in short, an oxyradical. Membranes isolated from mito chondria, endoplasmic reticulum, and plasma membrane have been recognized as able to catalyze the univalent reduction of oxygen to 0 2“ (1). Hydrogen perox ide is generated both as the product of 0 2" dismutation and as the product of two-electron transfer from flavin enzymes to the oxygen molecule. In mammalian cells most of the H20 2-producing enzymes are located in the peroxisomes (1,2).
