ABSTRACT
This chapter deals with the findings on various intrinsic antioxidant defense systems and their interrelationship in the cellular environment. Oxygen is required for normal metabolic reactions necessary to sustain life. Oxygen, however, especially its activated intermediates, may also react with cellular constituents with resultant degradation and/or inactivation of essential molecules. Extensive oxidation may lead to rupture of cellular membranes and release of destructive lysosomal enzymes and metal catalysts. The generation of hydroxyl radicals by transition metals from hydrogen peroxide produced by phagocytic cells and intracellular sources has been implicated as an important initiation mechanism for lipid peroxidation and cell injury. In view of the potential adverse effects of oxygen and its reactive intermediates, it is important that a number of enzymes/enzyme systems and compounds present in the cell may function to protect cellular componments from the deleterious effects of the activated oxygen species.
