Superoxide dismutase (SOD) is a metalloenzyme that catalyzes the dismutation of superoxide radicals into molecular oxygen and hydrogen peroxide. It contains two metal ions that are essential for its catalytic activity. The metal ions present in SOD are:

Cu (II) and Zn (II)

The metal ions are bound to the protein through a series of histidine residues and are arranged in a specific geometry that is crucial for the enzyme's activity. The Cu (II) ion is located at the active site, where it acts as a Lewis acid to facilitate the oxidation of the superoxide radical. The Zn (II) ion is located at the dimer interface and is involved in stabilizing the protein structure.

The role of Cu (II) and Zn (II) ions in SOD catalysis:

Cu (II) ion:

1. The Cu (II) ion undergoes a redox reaction with the superoxide radical, forming Cu (I) and superoxide anion.

2. The Cu (I) ion is then oxidized back to Cu (II) by another superoxide radical, completing the catalytic cycle.

3. The Cu (II) ion also acts as a Lewis acid, facilitating the oxidation of the superoxide radical.

Zn (II) ion:

1. The Zn (II) ion is involved in stabilizing the protein structure by coordinating with the histidine residues at the dimer interface.

2. The Zn (II) ion also helps to maintain the correct geometry of the active site, which is essential for SOD activity.

In conclusion, SOD contains Cu (II) and Zn (II) ions that are essential for its catalytic activity. The Cu (II) ion is located at the active site and facilitates the oxidation of the superoxide radical, while the Zn (II) ion stabilizes the protein structure and maintains the correct geometry of the active site.