SOD2

Function

SOD2 (manganese superoxide dismutase, MnSOD) converts mitochondrial superoxide (O₂⁻) into hydrogen peroxide, which is further detoxified by catalase and peroxidases. It is the primary antioxidant defense within mitochondria.

Knockout in mice is embryonic lethal; heterozygous knockout mitochondria accumulate damage and the mice are prone to cardiomyopathy and neurodegeneration.

The V16A variant

The V16A polymorphism affects the mitochondrial-targeting sequence:

• VV genotype: more efficient import into mitochondria, higher matrix activity.
• AA genotype: less efficient import.

Associations with cardiovascular disease, neurodegeneration, and certain cancers have been reported but effect sizes are modest and replication mixed.

Practical interpretation

• Not routinely tested clinically.
• Lifestyle and dietary antioxidants are unlikely to substantially modify SOD2 activity at the genotype level.
• Exercise upregulates SOD2 expression independent of genotype — one of the cellular mechanisms behind exercise’s longevity benefit.

Why it’s in this reference

SOD2 illustrates how individual antioxidant-gene variants have measurable but modest effects, and why "antioxidant supplementation" without targeting specific deficiencies has been disappointing in RCTs — the intracellular systems are tightly regulated.

Related entries

Mitochondrial dysfunction, Free radical theory, Exercise.