Amino acid metabolism: tyramine and monoamine oxidase inhibitors: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Amino acid metabolism: tyramine and monoamine oxidase inhibitors

Sample item

A depressed patient on phenelzine eats aged cheese and develops a throbbing headache and a hypertensive crisis. Which amine, formed by decarboxylation of an aromatic amino acid, has accumulated?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Tyramine

Tyramine, formed by decarboxylation of tyrosine, is normally destroyed by gut and liver monoamine oxidase. With an MAO inhibitor it is absorbed, enters nerve terminals and displaces stored noradrenaline, causing hypertension.

Option by option

  • A. Cadaverine

    Cadaverine arises from lysine decarboxylation during putrefaction and is not the pressor amine.

  • B. Histamine

    Histamine comes from histidine and causes flushing and scombroid-type reactions, not a pressor crisis.

  • C. Tyramine (correct)

    Correct. Tyramine from fermented foods releases catecholamines when MAO is blocked.

  • D. Gamma-aminobutyrate

    Gamma-aminobutyrate is an inhibitory neurotransmitter formed from glutamate, not an aromatic amine.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is C, Tyramine. Tyramine, formed by decarboxylation of tyrosine, is normally destroyed by gut and liver monoamine oxidase.

Why is "Cadaverine" not the answer?

Cadaverine arises from lysine decarboxylation during putrefaction and is not the pressor amine.

Why is "Histamine" not the answer?

Histamine comes from histidine and causes flushing and scombroid-type reactions, not a pressor crisis.

Why is "Gamma-aminobutyrate" not the answer?

Gamma-aminobutyrate is an inhibitory neurotransmitter formed from glutamate, not an aromatic amine.

What concept does this question test?

It tests Amino acid metabolism: tyramine and monoamine oxidase inhibitors in Biochemistry. With an MAO inhibitor it is absorbed, enters nerve terminals and displaces stored noradrenaline, causing hypertension.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Amino acid metabolism: tyramine and monoamine oxidase inhibitors?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.