[P002] Poster

1:00 PM - 1:50 PM JST(4:00 AM - 4:50 AM UTC)

[P01-138] Elucidation of the aspartate biosynthesis pathway in Thermococcus kodakarensis

○Yu Su¹, Yuta Michimori¹, Yuto Fukuyama², Shigeru Shimamura², Takuro Nunoura², Haruyuki Atomi¹ (1. Kyoto Univ. (Japan), 2. JAMSTEC (Japan))

Keywords:

archaea,metabolism,amino acid

In bacteria, aspartate can be synthesized from oxaloacetate by aspartate dehydrogenase or aspartate aminotransferase. The hyperthermophilic archaeon Thermococcus kodakarensis does not possess an aspartate dehydrogenase, but harbors four Class I aminotransferases encoded by TK0186, TK0548, TK1094 and TK2268. Among the four proteins, the TK2268 protein was the only protein to recognize oxaloacetate as the amino acceptor. With oxaloacetate, TK2268 protein only recognized glutamate as the amino donor. Aminotransferase activity between oxaloacetate and glutamate was observed in cell extracts of the T. kodakarensis host strain KU216. This activity was evaluated in the cell extracts of the individual gene disruption strains of the four aminotransferases, suggesting that the TK2268 protein was responsible for this activity. T. kodakarensis KU216 displays growth in synthetic amino acid medium supplemented with both oxaloacetate and glutamate. Although growth was maintained in ΔTK0186, ΔTK0548, and ΔTK1094, growth was not observed in the ΔTK2268 strain. The results suggest that TK2268 protein is the predominant aminotransferase responsible for the conversion of oxaloacetate to aspartate. The tracer-based metabolomics using ¹³C₃-pyruvate indicated that pyruvate is a precursor of aspartate, and that this conversion is dependent on TK2268 protein. T. kodakarensis does not harbor a tricarboxylic acid cycle, a common route for oxaloacetate generation, but enzymes involved in oxaloacetate biosynthesis have recently been identified. The study elucidates the complete aspartate biosynthesis pathway in T. kodakarensis and presents novel metabolic functions in hyperthermophilic archaea lacking the TCA cycle.