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.
Purine degradation & uric acid
Inosine
Made from Adenosine by Adenosine deaminase (ADA)
Adenosine deaminase (ADA) · irreversible — Purine degradation & uric acid
Deficiency: ADA deficiency → SCID (AR): adenosine/deoxyadenosine accumulate → dATP ↑ → ribonucleotide reductase inhibited → no dNTPs → T, B AND NK cells die; recurrent infections, no thymic shadow, fatal by ~2 y untreated; enzyme replacement, transplant, gene therapy
Lymphocytes have the highest ADA activity of any cell.
Condition cards:Adenosine deaminase (ADA) deficiency — SCID →
Made from IMP by 5′-Nucleotidase
5′-Nucleotidase — Purine degradation & uric acid
Becomes Hypoxanthine via Purine nucleoside phosphorylase (PNP)
Purine nucleoside phosphorylase (PNP) — Purine degradation & uric acid
Cofactors: Pi → ribose-1-P
Deficiency: PNP deficiency — milder, predominantly T-cell immunodeficiency (B cells relatively spared); supportive care / transplant
Condition cards:Purine nucleoside phosphorylase (PNP) deficiency →