Superoxide dismutase (SOD) is a hydroquinone oxidase, SOD activity being secondary to this component

What is it about?

Two field founding reactive oxygen species (ROS) scientist scientists (Fridovich & Joseph McCord) came to the conclusion that the detoxification of superoxide via the superoxide dismutase (SOD) activity was the primary function of this protein. This was a plausible conclusion at the time (1970s-1980s). However, I believe this conclusion is incorrect, with reference to cytosollic Cu/Zn SOD. Superoxide dismutation isn't its purpose and superoxide isn't the villain it was made out to be. The proposed enzymatic function of Cu/Zn SOD is as a ubiquinol oxidase. The SOD activity is likely a consequence of the necessary dismutation of superoxide, generated as an enzyme-bound intermediate during its activity. The low specificity of this enzyme for hydroquinones allowed it to oxidize a wide range of hydroquinone substrates. This would account for its elevated activity in cells expressing resistance against anticancer drugs like mitomycin C etc., which act via reduction to toxic hydroquinones.

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Photo by Hassaan Here on Unsplash

Photo by Hassaan Here on Unsplash

Why is it important?

Research into SOD, and relatively small synthetic molecules with SOD activity, has become a major research endeavor. This is largely due to their potential health and life extending properties assuming superoxide has significant cellular toxicities. However, the view that superoxide isn't an age accelerating villain, and SOD activity isn't the primary function of this protein, but its role as an ubiquinol oxidase (or general hydroquinone oxidase) may add a new twist to this research field.

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