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Metabolic pathways

Every FMK pathway as a clickable map. Pick one pathway to hammer it — next step, enzyme, regulator, cofactor, and the facts that get tested (NADPH and who needs it, rate-limiting steps, deficiencies) — or set it to all pathways for a mixed drill. Every answer says which enzyme and which pathway.

Pathway

Catecholamines, serotonin & the tyrosine tree · CNS and sympathetic ganglia (dopamine, NE); adrenal medulla only for epinephrine; melanocytes for melanin; liver for the degradation arm; serotonin in CNS raphe nuclei, gut enterochromaffin cells and platelets, with melatonin made from it in the pineal. Enzymes sit beside the arrows, ★ = rate-limiting, ⊕/⊖ = activators/inhibitors (toggle), −ATP +NADH = what the step spends and makes (toggle ⚡), dashed = allosteric signal, shaded bands = compartment. Drag to pan.

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Catecholamines, serotonin & the tyrosine tree

Vanillylmandelic acid (VMA)

Made from Normetanephrine by MAO (oxidative deamination) — normetanephrine → VMA

MAO (oxidative deamination) — normetanephrine → VMA — Catecholamines, serotonin & the tyrosine tree

Deficiency: MAO INHIBITORS block this enzyme, so norepinephrine and serotonin stay on their receptors longer — the antidepressant effect, and the reason for the tyramine interaction

Both arms converge here: normetanephrine and metanephrine are each finished by MAO to the same end product, VMA.

Condition cards:MAO inhibitors (MAOIs) →

Made from Metanephrine by MAO (oxidative deamination) — metanephrine → VMA

MAO (oxidative deamination) — metanephrine → VMA — Catecholamines, serotonin & the tyrosine tree

VMA in urine is the classic screen for a catecholamine-secreting tumour (pheochromocytoma) — the 24-hour urine VMA and metanephrines.