[2S05e] 12. Environmental Microbiology and Technology - Part 3

5:30 PM - 5:50 PM JST(8:30 AM - 8:50 AM UTC)

[2EMT-14] Unique C1 metabolism in the archaeon Thermococcus kodakarensis

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

Keywords:

metabolism,archaea,C1

The hyperthermophilic archaeon Thermococcus kodakarensis is an obligate anaerobe and heterotroph, utilizing a variety of organic compounds including amino acids, peptides and polysaccharides. We have been studying many aspects of metabolism in this organism, including the catabolism and biosynthesis of sugars, amino acids, nucleic acids and cofactors. Here we will focus on the enzymes involved in amino acid metabolism. In terms of catabolism, more than half of the twenty amino acids (Ala, Val, Ile, Leu, Met, Phe, Tyr, Trp, Glu/Gln, Cys, and His) are presumably degraded through aminotransferase or Glu dehydrogenase reactions to generate 2-oxoacids, which are subsequently converted to acyl-CoAs by 2-oxoacid:ferredoxin oxidoreductases and then to acids by NDP-forming acyl-CoA synthetases. Arginine catabolism occurs through a pathway including a recently identified enzyme designated arginine synthetase. In terms of aspartate and asparagine, indications of catabolic degradation are not present. T. kodakarensis grows in a medium without Asp and Asn in the presence of oxaloacetate and Glu. The aminotransferase responsible for the conversion of oxaloacetate and Glu to Asp and 2-oxoglutarate was identified. Due to the absence of a complete tricarboxylic acid cycle in T. kodakarensis, malate could not replace oxaloacetate as a precursor for Asp biosynthesis. Pyruvate was identified as a precursor for oxaloacetate, and the enzymes involved in the generation of oxaloacetate were identified.