**Core Concept**
Superoxide dismutase is an enzyme that catalyzes the dismutation of superoxide (O2−) into oxygen (O2) and hydrogen peroxide (H2O2). This enzyme plays a crucial role in protecting cells from oxidative damage caused by free radicals.

**Why the Correct Answer is Right**
Superoxide dismutase is a crucial antioxidant enzyme that helps maintain the balance of reactive oxygen species (ROS) in the body. In the brain, superoxide dismutase works by converting superoxide radicals into hydrogen peroxide, which is then broken down into water and oxygen by other enzymes. This process prevents the accumulation of superoxide radicals, which can cause cellular damage and contribute to neurodegenerative diseases. Superoxide dismutase is present in both the cytosol and the mitochondria of cells, allowing it to effectively neutralize superoxide radicals from multiple sources.

**Why Each Wrong Option is Incorrect**
**Option A:** Myeloperoxidase is an enzyme found in neutrophils that produces hypochlorous acid, a potent antimicrobial agent. While it has some antioxidant properties, it is not primarily involved in protecting the brain from free radical injury.
**Option B:** Monoamine oxidase (MAO) is an enzyme involved in the breakdown of neurotransmitters such as serotonin and dopamine. It is not directly related to the protection of the brain from free radical injury.
**Option D:** Hydroxylase enzymes are involved in the synthesis of various compounds, including steroids and amino acids. They do not protect the brain from free radical injury.

**Clinical Pearl / High-Yield Fact**
Superoxide dismutase is a key enzyme in maintaining the balance of ROS in the body, and its deficiency has been linked to various neurodegenerative diseases, including Alzheimer's and Parkinson's disease. Understanding the role of superoxide dismutase in protecting the brain from free radical injury is essential for appreciating the pathophysiology of these diseases.

✓ Correct Answer: C. Superoxide dismutase