Long-chain acyl-coenzyme A dehydrogenase deficiency: biochemical studies in fibroblasts from three patients.

We studied fibroblasts from three patients with long-chain acyl-coenzyme A dehydrogenase (LCADH) deficiency; siblings H.C. and J.C. had milder clinical phenotypes than unrelated patient R-1. In H.C., J.C., and R-1 oxidation of [9,10(n)-3H]palmitate was 50, 48, and 28% of control, respectively, with R-1 having significantly less activity than H.C. and J.C. (p less than 0.05). Assays of mitochondrial short-chain and medium-chain acyl-coenzyme A dehydrogenases were normal in H.C. and J.C. However, mitochondrial LCADH activities in all three ranged from 17 to 21% of control. Flavin adenine dinucleotide addition increased LCADH activities in all three to 27-36% of control. In the presence of monospecific medium-chain acyl-coenzyme A dehydrogenase antiseria, LCADH activity decreased 17% in controls, and fell to less than or equal to 11% of control in J.C. and R-1. The heterogeneity observed in the [3H]palmitate oxidation studies was not explained by differences in LCADH activities under any assay condition.