Learn / Metabolism

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

Sphingolipid degradation & the sphingolipidoses · Lysosome (degradation); synthesis in ER → Golgi. 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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Sphingolipid degradation & the sphingolipidoses

Galactocerebroside (Gal + ceramide)

Made from Sulfatide (galactocerebroside + sulfate) by Arylsulfatase A

Arylsulfatase A · irreversible — Sphingolipid degradation & the sphingolipidoses

Deficiency: Metachromatic leukodystrophy (AR, ARSA) — sulfatides accumulate: central and peripheral DEMYELINATION, ataxia, mental regression and psychiatric change; metachromatic granules in Schwann cells

Removes the sulfate from sulfated galactocerebroside. Sulfatides sit in brain and kidney.

Condition cards:Metachromatic leukodystrophy →

Becomes Ceramide (sphingosine + fatty acid) via Galactocerebrosidase (GALC)

Galactocerebrosidase (GALC) · irreversible — Sphingolipid degradation & the sphingolipidoses

Deficiency: Krabbe disease (AR, GALC) — galactocerebroside and the toxic metabolite psychosine accumulate: severe myelin loss, developmental regression, optic atrophy, peripheral neuropathy, GLOBOID cells

Also called galactosylceramidase. Its substrate is the main glycolipid of myelin, so the disease is a leukodystrophy.

Condition cards:Krabbe disease →