Clinical biochemistry: catecholamine metabolism: practice question

The best answer is D, Catechol-O-methyltransferase and monoamine oxidase. Catecholamines are inactivated by catechol-O-methyltransferase, which forms the metanephrines, and by monoamine oxidase followed by aldehyde dehydrogenase.

These enzymes build norepinephrine and epinephrine rather than break them down.

These enzymes make dopamine from tyrosine and are part of synthesis, not catabolism.

Phenylalanine hydroxylase converts phenylalanine to tyrosine and has no role in catecholamine breakdown.

It tests Clinical biochemistry: catecholamine metabolism in Biochemistry. Together they yield vanillylmandelic acid, the main urinary end-product. Plasma free or urinary fractionated metanephrines are the preferred screening tests in pheochromocytoma.

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.

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.

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.