論文

査読有り 国際誌
2021年5月3日

Identification and biochemical characterization of threonine dehydratase from the hyperthermophile Thermotoga maritima

Amino acids
  • Tetsuya Miyamoto
  • ,
  • Masumi Katane
  • ,
  • Yasuaki Saitoh
  • ,
  • Masae Sekine
  • ,
  • Kumiko Sakai-Kato
  • ,
  • Hiroshi Homma

記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1007/s00726-021-02993-x

The peptidoglycan of the hyperthermophile Thermotoga maritima contains an unusual component, D-lysine (D-Lys), in addition to the typical D-alanine (D-Ala) and D-glutamate (D-Glu). In a previous study, we identified a Lys racemase that is presumably associated with D-Lys biosynthesis. However, our understanding of D-amino acid metabolism in T. maritima and other bacteria remains limited, although D-amino acids in the peptidoglycan are crucial for preserving bacterial cell structure and resistance to environmental threats. Herein, we characterized enzymatic and structural properties of TM0356 that shares a high amino acid sequence identity with serine (Ser) racemase. The results revealed that TM0356 forms a tetramer with each subunit containing a pyridoxal 5'-phosphate as a cofactor. The enzyme did not exhibit racemase activity toward various amino acids including Ser, and dehydratase activity was highest toward L-threonine (L-Thr). It also acted on L-Ser and L-allo-Thr, but not on the corresponding D-amino acids. The catalytic mechanism did not follow typical Michaelis-Menten kinetics; it displayed a sigmoidal dependence on substrate concentration, with highest catalytic efficiency (kcat/K0.5) toward L-Thr. Interestingly, dehydratase activity was insensitive to allosteric regulators L-valine and L-isoleucine (L-Ile) at low concentrations, while these L-amino acids are inhibitors at high concentrations. Thus, TM0356 is a biosynthetic Thr dehydratase responsible for the conversion of L-Thr to α-ketobutyrate and ammonia, which is presumably involved in the first step of the biosynthesis of L-Ile.

リンク情報
DOI
https://doi.org/10.1007/s00726-021-02993-x
PubMed
https://www.ncbi.nlm.nih.gov/pubmed/33938999
ID情報
  • DOI : 10.1007/s00726-021-02993-x
  • PubMed ID : 33938999

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