Friedreich's ataxia in Northern Italy. II. Biochemical studies in cultured cells

Pyruvate and palmitate oxidations by cultured fibroblast suspensions were measured in optimized conditions and proved to be within normal range in the cells from Friedreich's patients. However, when pyruvate oxidation was measured by direct assay of the pyruvate dihydrogenase complex, this enzyme activity proved to be significantly lower in Friedreich's than in controls' cells. These abnormalities were not observed when the cells were sonicated. Moreover, lipoamide dehydrogenase activity, Km and Vmax were within the normal range in Friedreich's cells. These data suggest that the low activities of the PDH complex are not a primary defect in Friedreich's ataxia, but are more likely related to membrane abnormalities in Friedreich's cells.