[Specific enzyme diagnosis in mitochondrial myopathies and encephalomyopathies].

Mitochondrial enzyme activities (cytochrome c-oxidase = COX, carnitine acyl-transferase = CAT, citrate synthase = CS, lipoamide dehydrogenase = lipDH from the pyruvate-dehydrogenase complex, lactate dehydrogenase = LDH, and malate-dehydrogenase = MDH) were measured from progressive myopathy/encephalomyopathy. Cytochrome oxidase (COX) deficiency was detected from muscle or liver tissues, adult type of COX defectus had been diagnosed in 1 case and infantile type in further 6 cases. The 3 familial atactic children showed decreased activity of carnitine acetyl-transferase, too.

Isolation and characterization of carnitine acetyltransferase from S. cerevisiae.

Carnitine acetyltransferase was isolated from yeast Saccharomyces cerevisiae with an apparent molecular weight of 400,000. The enzyme contains identical subunits of 65,000 Da. The Km values of the isolated enzyme for acetyl-CoA and for carnitine were 17.

Kinetic advantage of the interaction between the fatty acid beta-oxidation enzymes and the complexes of the respiratory chain.

Respiration-linked oxidation of 3-hydroxybutyryl-CoA, crotonyl-CoA and saturated fatty acyl (C4, C8 and C14)-CoA esters was studied in different mitochondrial preparations. Oxidation of acyl-CoA esters was poor in intact mitochondria; however, it was significant, as well as, NAD+ and CoA-dependent in gently and in vigorously sonicated mitochondria. The respiration-linked oxidation of crotonyl-CoA and 3-hydroxybutyryl-CoA proceeded at much higher rates (over 700%) in gently disrupted mitochondria than in completely disrupted mitochondria.

Surplus acylcarnitines in the plasma of starved rats derive from the liver.

The method used here to assess the contribution of liver to plasma acylcarnitine is based on the idea that in rat, shortly after administration of [3H]butyrobetaine the [3H]carnitine appearing in the plasma derives from the liver and so does the acyl moiety of [acyl-3H] carnitine. In the perchloric acid extracts of plasma and liver, the ester fraction of total carnitine was determined by enzymatic analysis and that of [3H]carnitines was determined by high performance liquid chromatography. The ester fraction of total carnitine in the plasma of fed rats was 32.

Role of the liver in carnitine metabolism: the mechanism of development of carnitine-deficient status in guinea-pigs.

It was shown that carnitine deficiency and an impairment of the conversion of butyrobetaine into carnitine develops not only in ascorbic acid-deficient guinea-pigs but also in partially starved animals. We propose that the same mechanism, an absolute or relative ascorbic acid deficiency, is operating in both nutritional states. An increased urinary excretion greatly contributes to the development of carnitine deficiency in guinea-pigs, both in ascorbic acid deficiency and starvation.