**Core Concept**
Norepinephrine, a catecholamine neurotransmitter, is metabolized through two primary enzyme-catalyzed pathways: monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). Understanding the role of these enzymes is crucial in pharmacology, particularly in the context of treating hypertension and other cardiovascular disorders.

**Why the Correct Answer is Right**
Norepinephrine is first metabolized by MAO, which breaks down the amine group, resulting in the formation of aldehyde. This aldehyde is then further metabolized by COMT, which methylates the aldehyde to form vanillylmandelic acid (VMA), a major metabolite of norepinephrine. This dual metabolic pathway is essential for regulating norepinephrine levels in the body. MAO inhibitors, such as phenelzine, and COMT inhibitors, such as entacapone, are used in the management of Parkinson's disease and other disorders.

**Why Each Wrong Option is Incorrect**
**Option A:** COMT is indeed involved in the metabolism of norepinephrine, but it is not the sole enzyme responsible for its metabolism.
**Option B:** MAO is also crucial in the metabolism of norepinephrine, but like COMT, it is not the only enzyme involved.
**Option D:** This option is incorrect as both MAO and COMT are indeed enzymes involved in the metabolism of norepinephrine.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that MAO inhibitors can cause a dangerous interaction with tyramine-rich foods, such as aged cheese and red wine, leading to a hypertensive crisis.

**Correct Answer:**
✓ Correct Answer: C. Both