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

Purine synthesis & salvage · Cytosol — de novo mainly liver; salvage matters most in brain, marrow and RBCs. Enzymes sit beside the arrows; a ★ marks the rate-limiting step. The map scrolls inside its panel.

Zoom

Purine synthesis & salvage

AMP

Made from IMP by Adenylosuccinate synthetase → adenylosuccinase

Adenylosuccinate synthetase → adenylosuccinase — Purine synthesis & salvage

Cofactors: Aspartate, GTP → GDP

Inhibited by: AMP (feedback on its own branch)

GTP is required to make AMP — cross-regulation balances the pools.

Made from Adenine (salvage) by APRT (adenine phosphoribosyltransferase)

APRT (adenine phosphoribosyltransferase) — Purine synthesis & salvage

Cofactors: PRPP → PPi

Deficiency: APRT deficiency — rare; adenine is oxidised to 2,8-dihydroxyadenine → kidney stones; far milder than HGPRT deficiency

Condition cards:APRT (adenine phosphoribosyltransferase) deficiency →

Becomes ADP / GDP (NDP) via Base-specific NMP kinase (adenylate / guanylate kinase)

Base-specific NMP kinase (adenylate / guanylate kinase) — Purine synthesis & salvage

Cofactors: ATP

Does not discriminate ribose from deoxyribose substrates.