Abnormal enzyme activity in cultured fibroblasts Reduced branched-chain alpha-keto acid dehydrogenase activity in cultured fibroblasts 2023-09-17T21:59:46Z Branched-chain alpha-keto acid dehydrogenase complex is an inner-mitochondrial enzyme complex that catalyzes the oxidative decarboxylation of the branched-chain alpha-ketoacids derived from isoleucine, leucine, and valine. Activity of branched-chain alpha-keto acid dehydrogenase complex (EC 1.2.4.4) below the lower limit of normal in cultured fibroblasts.