Polyacrylamide-gel-electrophoretic analysis of cultured skin fibroblasts from patients with Duchenne muscular dystrophy.

2-Oxoisovalerate palmitoylcarnitine and 2-oxoisovalerate were 1 .O, 0.3 and 0.07 respectively. The rate of oxidation of 2-oxoisovalerate determined spectrophotometrically was about 12 times faster than when measured at 30°C by "CO, release from 2-0xo[ 114C]isovalerate by rat liver mitochondria1 fractions (Bremer & Davis, 1978; Patel et al., 1980). a-Cyano-4-hydroxycinnamate specifically inhibits pyruvate uptake by mitochondria (Halestrap et al., 1980). There was no inhibition of the oxidation of 0.5 mM-2-OXOiSOValerate by 100 j~-a-cyano-4-hydroxycinnamate nor by 10 mM-pyruvate under our experimental conditions, in apparent disagreement with other reports (Halestrap et al., 1980; Patel et al., 1980). This leaves unanswered the question of the nature of the carriers by which 2-oxoisovalerate enters the mitochondrial matrix. Direct spectrophotometric measurements of branched-chain 2-0x0 acid dehydrogenase with 2-oxoisovalerate as substrate will be useful to study the activity of this enzyme in liver in different hormonal and nutritional conditions.