Similarity of the E1 subunits of branched‐chain‐oxoacid dehydrogenase from Pseudomonas putida to the corresponding subunits of mammalian branched‐chain‐oxoacid and pyruvate dehydrogenases

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Abstract
The genes encoding proteins responsible for activity of the E1 component of branched‐chain‐oxoacid dehydrogenase of Pseudomonas putida have been subcloned and the nuckotide sequence of this region determined. Open reading frames encoding E1α (bkdA1, 1233 bp) and E1β (bkdA2, 1020 bp) were identified with the aid of the N‐terminal sequence of the purified subunits. The Mr of E1α was 45158 and of E1β was 37007, both calculated without N‐terminal methionine. The deduced amino acid sequences of E1α and E1β had no similarity to the published sequences of the E1 subunits of pyruvate and 2‐oxoglutarate dehydrogenases of Escherichia coli. However, there was substantial similarity between the E1α subunits of Pseudomonas and rat liver branched‐chain‐oxoacid dehydrogenases. In particular, the region of the E1α subunit of the mammalian branched‐chain‐oxoacid dehydrogenase which is phosphorylated, was found to be highly conserved in the Pseudomonas E1α subunit. There was also considerable similarity between the E1β subunits of Pseudomonas branched‐chain‐oxoacid dehydrogenase and human pyruvate dehydrogenase.