Which enzyme is responsible for breaking down tyramine?

The correct choice is MAO-A, which stands for monoamine oxidase A. This enzyme plays a crucial role in the metabolism of various monoamines, including tyramine, by catalyzing their oxidative deamination. Tyramine is mainly found in certain foods and can interact with monoamine neurotransmitters in the body.

MAO-A specifically targets tyramine and other biogenic amines, facilitating their breakdown and preventing excessive accumulation, which is particularly important in managing dietary tyramine levels that can affect blood pressure and cardiovascular health. This is especially relevant for patients on certain monoamine oxidase inhibitors (MAOIs) for psychiatric conditions; they must adhere to dietary restrictions to prevent hypertensive crises due to the build-up of tyramine.

In contrast, while MAO-B is also involved in the metabolism of monoamines, it does not primarily break down tyramine. COMT (catechol-O-methyltransferase) is involved in the metabolism of catecholamines, and dopamine decarboxylase is an enzyme important in the synthesis of dopamine but does not engage in the degradation of tyramine. Understanding the specific roles of these enzymes is crucial in pharmacology, especially when considering drug interactions and dietary factors in patient care.