Lysine is synthesized through the alpha-aminoadipate pathway in Thermus thermophilus.
A 3.8-kb DNA fragment which was able to complement the mutation of a lysine auxotrophic Thermus thermophilus mutant was cloned from T. thermophilus HB27. Sequence analysis of the 3.8-kb fragment indicated the presence of three open reading frames including a truncated one. The predicted amino acid sequences of two of the three open reading frames showed 55.2% and 45.0% identity with homocitrate synthase and homoaconitate hydratase of Saccharomyces cerevisiae, respectively. These two enzymes act as lysine biosynthetic enzymes through the alpha-aminoadipate pathway which has been reported in S. cerevisiae and fungi. Each of the two open reading frames in T. thermophilus was disrupted by integration of the heat-stable kanamycin nucleotidyltransferase gene. The resulting mutants showed lysine auxotrophy, which could be complemented with alpha-aminoadipate but not with diaminopimelate. These results indicate that lysine was synthesized through the alpha-aminoadipate pathway and not through the diaminopimelate pathway in T. thermophilus.
Kosuge
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Institute of Applied Biochemistry, University of Tsukuba, Ibaraki, Japan.
Hoshino
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D015074:2-Aminoadipic Acid / Q000378:metabolism*; D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D005798:Genes, Bacterial / Q000235:genetics; D005800:Genes, Fungal; D006836:Hydro-Lyases / Q000378:metabolism; D008239:Lysine / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames / Q000235:genetics; D007652:Oxo-Acid-Lyases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D016415:Sequence Alignment; D016963:Thermus thermophilus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D015074:2-Aminoadipic Acid; C021365:homocitrate synthase; D007652:Oxo-Acid-Lyases; D006836:Hydro-Lyases; C107855:homoaconitate hydratase; D008239:Lysine