Regulation of Citrate Efflux from Mitochondria of Oleaginous and Non‐Oleaginous Yeass by Long‐Chain Fatty Acyl‐CoA Esters

Citrate efflux from a wide range of yeast mitochondria was inhibited by long-chain fatty-acyl-CoA esters. 2. Fatty-acyl-CoA esters with chain lengths of between 14 and 18 carbons were the most potent inhibitors of citrate efflux which was unaffected by the fatty acids themselves. 3. 50% inhibition of citrate transport was observed using palmitoyl-CoA and oleoyl-CoA at approx. 4-5 microM when the tricarboxylate carrier was saturated with L-malate as counter-anion. 4. The inhibition with palmitoyl-CoA and oleoyl-CoA was competitive with L-malate. 5. The possibility that the fatty-acyl-CoA esters were exerting their effect by acting as detergent was eliminated because of the low concentrations used and appropriate comparisons being made with non-specific detergents. Although detergents inhibited citrate efflux they also released citrate by causing membrane damage. 6. The effect of fatty-acyl-CoA esters on citrate efflux could be decreased by using higher mitochondrial protein levels and by adding bovine serum albumin. 7. The possibility is discussed that this inhibition represents a genuine feedback inhibition which could regulate the amount of lipid being synthesized by an oleaginous yeast.