Branched chain α-keto acid dehydrogenase in tissues from rainbow trout (Salmo gairdnerii)

Mitochondria isolated from skeletal red muscle of rainbow trout (Salmo gairdnerii) have remarkably high activity of branched chain alpha-keto acid dehydrogenase as measured with alpha-keto isocaproic acid as substrate. The activity of the dehydrogenase increases several-fold after preincubation of the mitochondria with an uncouple and oligomycin. The accumulation of the first product, isovaleryl-CoA is strongly stimulated by high concentrations of CoASH. In the crude mitochondrial lysates we have used, an unknown compound accumulates with time, during incubation with alpha-keto isocaproic acid, CoASH and NAD. The compound, probably a CoA derivative, is more hydrophobic than isovaleryl-CoA.