In peroxisomal beta-oxidation, very long chain fatty acids (VLCFAs, >C22) are oxidized by a distinct mechanism. A patient with Zellweger syndrome has absent peroxisomes and accumulates VLCFAs. Unlike mitochondrial beta-oxidation, the first oxidation step in peroxisomal beta-oxidation uses which electron acceptor?
- A NAD+
- B FAD (acyl-CoA oxidase generates H2O2) ✓
- C Ubiquinone (coenzyme Q)
- D Molecular oxygen directly (monooxygenase reaction)
Explanation
In peroxisomal beta-oxidation, the first oxidation step is catalyzed by acyl-CoA oxidase (also called palmitoyl-CoA oxidase), which directly reduces FAD and transfers electrons to molecular oxygen, producing H2O2 (hydrogen peroxide). This H2O2 is then neutralized by catalase within the peroxisome. This is fundamentally different from mitochondrial beta-oxidation, where acyl-CoA dehydrogenase reduces FAD and electrons enter the electron transport chain via electron transfer flavoprotein (ETF), generating ATP. The peroxisomal first step wastes the potential energy of those electrons as heat rather than coupling to ATP synthesis. This distinction explains why peroxisomal fatty acid oxidation is less efficient for ATP production than mitochondrial oxidation.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.