Comparison of Superoxide Dismutase Activity at the Cell, Organ, and Whole-Body Levels

Superoxide dismutase (SOD) can be considered an antitoxic metalloenzyme that facilitates the production of oxygen and hydrogen peroxide from superoxide anions. Four classes have been identified depending on selective binding of metals, namely Cu,Zn-SOD, Fe-SOD, Mn-SOD, and Ni-SOD. The established isoforms are SOD1, SOD2, and SOD3 in various cells and tissues of eukaryotes. The relatively newer type Ni-SOD binds nickel and is observed in bacteria, including the genus Streptomyces. The Fe-SOD and Mn-SOD are also present in bacteria. Cu,Zn superoxide dismutase (SOD1) activity correlates with various pathophysiological states of organs. SOD2 binds manganese (Mn) and is located in the mitochondria. The SOD3, similar to the SOD1, binds copper and zinc, which are also expressed in the brain. The assay relies on several methods, including the enzyme activities, expression, field potential, and patch-clamp electrophysiology. The effects of SOD activity are emphasized at organ and whole-body levels depending on animal models. The antioxidant properties and behavior of SOD are compared based on responses among females and males to diet and toxic substances. However, in humans with amyotrophic lateral sclerosis (ALS), the mean SOD activity in both erythrocytes and muscles was comparable to controls. The detailed comparisons between the catalase and SOD activities are one of the aspects of this review. Also, modulation of excitability and synaptic plasticity in neurons by SOD is highlighted.