USA Biology Olympiad (USABO) Practice Exam

In the context of superoxide dismutase 1, what role does copper play in the enzyme's function?

1. Activator

2. Inhibitor

3. Substrate

4. Cofactor

The correct answer is: Cofactor

Superoxide dismutase 1 (SOD1) is an important enzyme that catalyzes the conversion of superoxide radicals into hydrogen peroxide and molecular oxygen, thereby playing a vital role in cellular defense against oxidative stress. Copper acts as a cofactor in the enzyme's activity, which means it is an essential component that must be present for the enzyme to function properly. In SOD1, copper ions facilitate the catalytic activity of the enzyme by contributing to the redox reactions involved in the dismutation of superoxide. Specifically, copper alternates between reduced and oxidized states as it interacts with superoxide, which is critical for the enzyme's ability to catalyze its reaction efficiently. The relationship between the enzyme and copper is integral – without copper, SOD1 cannot carry out its protective function, leading to an accumulation of superoxide that can cause cellular damage. Thus, classifying copper as a cofactor accurately reflects its essential role in the catalytic mechanism of superoxide dismutase 1.