Biochemistry · Enzyme
Medium-chain acyl-CoA dehydrogenase (MCAD) !
MCAD carries out the first β-oxidation step for fatty acids of 6 to 12 carbons; its lack is the most common defect in the group.
Updated 2026-11-01
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Key facts
- Tetrameric flavoprotein of the mitochondrial matrix; uses FAD and hands electrons to ETF.
- Acts on medium-chain acyl-CoA (C6–C12), most active on octanoyl-CoA (C8).
- Family: VLCAD (very long chain, membrane-bound), LCAD, MCAD and SCAD (short).
- Most frequent variant in people of European ancestry: c.985A>G (p.Lys329Glu).
Regulation
- Its expression rises during fasting via PPARα.
- No major allosteric control; it follows substrate flow.
Inhibitors and toxins
- MCPA-CoA, a metabolite of ackee hypoglycin A
Clinical notes
- MCAD deficiency: hypoketotic hypoglycaemia, vomiting and lethargy with fasting or infection; high octanoylcarnitine (C8) on screening.
- Ackee poisoning inhibits MCAD and SCAD and mimics the picture.
Pathways
Related conditions
Related
Test yourself
Think of the answer, then tap the question to see it.
Which acylcarnitine is raised in MCAD deficiency?
Octanoylcarnitine (C8), together with C6 and C10:1.
Which coenzyme does MCAD use and where do its electrons go?
FAD; it passes them to electron transfer flavoprotein (ETF) and then to ubiquinone.
Which natural toxin inhibits MCAD?
MCPA-CoA, derived from hypoglycin A in unripe ackee fruit.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: ACADM: Medium-chain specific acyl-CoA dehydrogenase, mitochondrial (human) (UniProt, 2026); ACADM gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); 1EGC: Structure of T255E, E376G mutant of human medium chain acyl-CoA dehydrogenase complexed with octanoyl-CoA (RCSB Protein Data Bank, 2026).
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