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Abstract

Pyruvate and 2‐oxoglutarate dehydrogenase complexes are strongly inhibited by phytanoyl‐CoA (IC50 ≈ 10−6–10−7 M). Palmitoyl‐CoA is 10‐fold less potent. Phytanic or palmitic acids have no inhibitory effect up to 0.3 mM. At the substrate saturation, the acyl‐CoA's affect the first and second enzymatic components of the 2‐oxoglutarate dehydrogenase complex, while the third component is inhibited only at a low saturation with its substrate dihydrolipoamide. Thus, key regulatory branch points of mitochondrial metabolism are targets of a cellular derivative of phytanic acid. Decreased activity of the complexes might therefore contribute to neurological symptoms upon accumulation of phytanic acid in Refsum disease.