Beta-oxidation enzymes in normal human muscle and in muscle from a patient with an unusual form of myopathic carnitine deficiency.
In a reported patient with myopathic carnitine deficiency, addition of exogenous carnitine to muscle homogenates failed to correct palmitate oxidation, and oral carnitine was of no clinical benefit. In a muscle biopsy from this patient, we found that, in contrast to the marked deficiency of free carnitine (3% of normal) short- and medium-chain acylcarnitines were in the normal range and long-chain acylcarnitine was increased almost four times. As this result confirmed the hypothesis of a muscle defect of mitochondrial oxidation of palmitate, all eight enzymes of beta-oxidation were measured spectrophotometrically in the muscle extract. None of them was found to be defective. These data suggest that the underlying biochemical abnormality in this patient may be a deficiency of the carnitine-acylcarnitine translocase system or a defective interaction between acyl-CoA dehydrogenase and its flavoprotein coenzyme.