Friedreich ataxia. II. Normal kinetics of lipoamide dehydrogenase.

Lipoamide dehydrogenase (LAD) kinetic values, Km and Vmax, were normal in 11 patients with Friedreich ataxia. Fibroblast activities of the pyruvate and alpha-ketoglutarate dehydrogenase complex, and LAD activities, were also normal. There was no reduction in oxidative decarboxylation of pyruvate, alpha-ketoglutarate, or several other substrates in intact fibroblasts. Methodologic differences may account for differences of opinion about putative abnormalities of the alpha-ketoacid dehydrogenase complexes.