H. influenzae Rd and H. somnus 129Pt had genes encoding components of the pathways for leucine, isoleucine and valine synthesis. H. ducreyi 35000HP was missing all of the components of these pathways except sdaA, which encodes L-threonine deaminase I / L-serine ammonia-lyase. The first three steps for degradation of leucine, isoleucine and valine are the same (8), and H. influenzae Rd and H. somnus 129Pt had the gene ilvE, encoding branched-chain amino acid transaminase that performs the first step, but did not have the rest of the pathway genes.
As reported previously, H. influenzae Rd has homologs of all of the essential E. coli genes for the metabolism of histidine, glycine, serine, alanine, proline, phenylalanine, tyrosine and tryptophan (43). H. ducreyi 35000HP did not have any of the genes for histidine biosynthesis, and H. somnus 129Pt was missing all of the histidine biosynthesis genes except hisC. H. ducreyi 35000HP was also missing glyA and serA, which are involved in glycine and serine biosynthesis, respectively (8). None of the three organisms had the gene avtA, whose product converts L-valine to L-alanine (47). H. ducreyi 35000HP also did not have the genes to make proline from alpha-ketoglutarate or L-glutamate. All three of the organisms had the pheA and tyrA genes involved in both phenylalanine and tyrosine biosynthesis, but none of them had the tyrB gene, which is involved in the synthesis of L-tyrosine (8). In terms of tryptophan biosynthesis, H. influenzae Rd had genes encoding all of the components of the pathway from chorismate to L-tryptophan, while H. somnus 129Pt and H. ducreyi 35000HP each had one copy of trpG, which converts chorismate to anthranilate (8), and H. influenzaeRd had two copies of trpG.
