Leucine degradation pathway in mitochondria. The enzyme names are in blue, gene names in black/red [see Additional file 1] [42, 84]. Genes that are co-expressed are depicted in red font. BCAT, branched-chain amino acid aminotransferase; BCKDH (BCKDC), branched-chain alpha-keto acid dehydrogenase; IVD, isovaleryl-CoA dehydrogenase; MCC, methylcrotonyl-CoA carboxylase; MG-CoAH (E-CoAH), methylglutaconyl-CoA hydratase (enoyl-CoA hydratase); HMG-CoAL, hydroxymethylglutaryl-CoA lyase. The candidate genes for enzymes catalyzing two terminal reactions have not been identified.