A novel L-isoleucine metabolism in Bacillus thuringiensis generating (2S,3R,4S)-4-hydroxyisoleucine, a potential insulinotropic and anti-obesity amino acid

Appl Microbiol Biotechnol. 2011 Mar;89(6):1929-38. doi: 10.1007/s00253-010-2983-7. Epub 2010 Nov 11.


4-Hydroxyisoleucine (HIL) found in fenugreek seeds has insulinotropic and anti-obesity effects and is expected to be a novel orally active drug for insulin-independent diabetes. Here, we show that the newly isolated strain Bacillus thuringiensis 2e2 and the closely related strain B. thuringiensis ATCC 35646 operate a novel metabolic pathway for L-isoleucine (L-Ile) via HIL and 2-amino-3-methyl-4-ketopentanoic acid (AMKP). The HIL synthesis was catalyzed stereoselectively by an α-ketoglutaric acid-dependent dioxygenase and to be useful for efficient production of a naturally occurring HIL isomer, (2S,3R,4S)-HIL. The (2S,3R,4S)-HIL was oxidized to (2S,3R)-AMKP by a NAD(+)-dependent dehydrogenase. The metabolic pathway functions as an effective bypass pathway that compensates for the incomplete tricarboxylic acid (TCA) cycle in Bacillus species and also explains how AMKP, a vitamin B(12) antimetabolite with antibiotic activity, is synthesized. These novel findings pave a new way for the commercial production of HIL and also for AMKP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus thuringiensis / genetics
  • Bacillus thuringiensis / metabolism*
  • Biosynthetic Pathways / genetics*
  • Coenzymes / metabolism
  • Dioxygenases / genetics
  • Dioxygenases / metabolism
  • Isoleucine / analogs & derivatives*
  • Isoleucine / biosynthesis*
  • Keto Acids / metabolism
  • NAD / metabolism
  • Oxidation-Reduction
  • Oxidoreductases / metabolism
  • Pentanoic Acids / metabolism


  • 4-hydroxyisoleucine
  • 4-oxopentanoic acid
  • Coenzymes
  • Keto Acids
  • Pentanoic Acids
  • Isoleucine
  • NAD
  • Oxidoreductases
  • Dioxygenases